IC-NRLF 


ST    LESSONS 


ON 


NATURAL  IIIILOSOPHY, 


PART      SECOND 


HABTFOBD: 

TLLIAM  j.  HAMEBSLEY, 

PUFLISHEF. 


THE  LIBRARY 

OF 
THE  UNIVERSITY 

OF  CALIFORNIA 


PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


FIRST  LESSONS 


NATUBAL    PHILOSOPHY, 

FOR   CHILDREN. 


|n 

PART    SECOND. 


BY  MARY  A.   SWJJT. 

NEW     EDITION,     ENLARGED     AND    IMPROVED. 

HARTFORD: 

WILLIAM  J.    HAMERSLEY,    PUBLISHER. 
PHILADELPHIA    J.  B    L1PPINCOTT  &  CO. 
1862. 


V 


ENTERED  according  to  Act  of  Congress,   in  the  year  1859,  "by 
WILLIAM    J.     HAMERSLET, 

In  the  Clerk's  Office  of  the  District  Court  of  the  United  States 
for  the  District  of   Connecticut. 


R.  H.  HOBBS, 
STEREOTYPER  AND  ELECTROTYPER. 


THE  favorable  reception  given  to  the  "  FIRST 
PART  OF  LESSONS  ABOUT  NATURAL  PHILOSOPHY," 
encouraged  the  writer  to  offer  to  parents  and  teach- 
ers of  primary  schools,  the  "SECOND  PART." 

It  was  received  with  the  same  approbation  ex- 
tended to  its  predecessor,  and  is  now  respectfully 
presented  in  an  enlarged  and  improved  form. 


M35S76S 


t  HAT  does  Natural  Philos- 
ophy teach  us  ? 

It  teaches  us  about 
the  matter  that  all  bod- 
ies   are   made  of,   and 
about  the  properties  of 
bodies. 

What  is  a  BODY  ? 
A  body  is  any  thing  made  of  matter. 
You  have  learned  about  the  Attraction  of 
Cohesion — is  this  property  found  in  all  bodies? 
It  is ;  but  it  is  stronger  in  some  bodies  than 
it  is  in  others. 

In  what  bodies  is  it  the  strongest  ? 
In  hard  bodies. 


6  BODIES. 


Do  we  call  hard  bodies  by  any  other  name  ? 

We  call  them  solid  bodies,  or  solids. 

Can  you  mention  some  solid  bodies  ? 

Wood,  and  stone,  and  iron  are  solid  bodies. 

Are  cork  and  sponge  solid  bodies  ? 

They  are. 

But  they  are  SOFT  bodies — are  SOFT  bodies 
solids  ? 

They  are. 

Why  are  some  solids  HARD,  and  other  solids 
soft?  ^ 

Because  the  attraction  of  cohesion  is 
stronger  in  hard  bodies  than  in  soft  bodies. 

What  do  you  mean  by  the  attraction  of  co- 
hesion ? 

The  attraction  of  cohesion  is  the  power  of 
sticking  together,  which  God  has  given  to  the 
little  particles  of  bodies. 

If  you  make  clay  and  dough  into  any  shape, 
why  will  they  remain  in  that  shape  ? 

Because  they  are  solid  bodies. 


LIQUIDS. 


Why  could  you  not  make  milk  and  oil  into 
any  shape  ? 

Because  they  are  not  solid  bodies. 

What  are  they  called  ? 

They  are  called  Liquids. 

If  I  should  place  a  solid  and  a  liquid  upon  a 
table,  how  could'  you  tell  which  was  the  SOLID  ? 

The  solid  would  remain  upon  the  table  as 
you  placed  it. 

What  would  the  LIQUID  do  ? 

It  would  flow  on  the  table,  or  down  from 
the  table  to  the  floor. 

Why  would  the  liquid  act  so  differently  from 
the  solid  ? 

Because  the  attraction  of  cohesion  is  so 
much  stronger  in  the  solid,  and  keeps  the 
particles  close  together. 

Do  the  particles  of  liquids  attract  each  other 
at  all  ? 

They  do. 

How  do  we  know  they  do  ? 

If  I  dip  my  finger  in  a  liquid,  when  I  take 


8  FLUIDS. 


it  out,  a  drop  will  stay  on  the  -end  of  my 
finger. 

What  makes  the  shape  of  drops  of  rain  and 
dew  ? 

The  attraction  of  cohesion,  that  draws  to- 
gether the  little  particles  of  water. 

What  is  a  LIQUID? 

A  Liquid  is  something  that  flows  like  water. 

Have  liquids  any  other  name  ? 

They  have ;  they  are  sometimes  called 
Fluids. 

Do  all  FLUIDS  flow  like  water  1 

Not  all ;  there  are  some  fluids  that  are  dif- 
ferent from  water  and  oil. 

Are  steam  and  air  solids  ? 

They  are  not. 

How  do  you  know  they  are  not  ? 

Because  they  do  not  keep  their  place,  and 
can  not  be  made  into  any  shape. 

Are  they  liquids  ? 

They  are  not. 

How  do  you  knorv  they  are  not  ? 


FLUIDS.  9 


Because  they  do  not  flow  down  to  the 
ground,  like  water. 

What  are  such  bodies  as  air  and  steam 
called  ? 

They  are  called  Aeriform  fluids. 

What  is  the  meaning  of  AERIFORM  ? 

Air- form. 

Why  is  steam  called  aeriform  ? 

Because  it  is  like  air. 

Can  you  tell  the  difference  between  liquids 
and  aeriform  fluids  ? 

Liquids  only  move  in  one  direction,  that 
is,  downward,  from  a  higher  to  a  lower 
place. 

How  do  fluids  like  air  move  ? 

They  can  move  as  easily  in  one  direction 
as  in  another. 

What  fluids  do  we  see  move  upward? 

The  fog  rises  up,  and  helps  to  form  the 
clouds,  and  steam  rises  from  the  engine  and 
floats  away. 

How  is  it  with  smoke  ? 


10 


FLUIDS.     DENSITY. 


Smoke  rises  from  the  chimney,  and  flames 
rise  from  burning  bodies. 


How  many  kinds  of  fluids  are  there  ? 

Two ;  liquids  and  aeriform  fluids. 

Then  how  many  kinds  of  BODIES  are 
there  ? 

Three ;  solids,  liquids,  and  aeriform  bod- 
ies. 

What  do  we  call  HEAVY  solid  bodies  ? 

We  call  them  dense  bodies. 


DENSITY.     RARITY.  H 

What  is  DENSITY  ? 

Density  means  heaviness. 

What  bodies  are  dense  ? 

Those  bodies  whose  particles  are  close  to- 
gether, are  dense. 

What  causes  their  particles  to  cling  together 
so  closely  ? 

The  attraction  of  cohesion. 

Can  you  mention  some  DENSE  bodies  ? 

Gold,  and  iron,  and  stones  are  dense. 

Which  has  the  greatest  density,  iron  or 
wood  ? 

Iron  has  the  greatest  density ;  it  is  the 
heaviest. 

What  do  we  call  light  solid  bodies  ? 

We  call  them  rare,  or  thin  bodies. 

What  is  RARITY  ? 

Rarity  is  thinness,  or  lightness. 

What  bodies  are  RARE  ? 

Those  bodies  whose  particles  are  not  at- 
tracted strongly  together. 

Can  you  mention  any  such  bodies  ? 


12  RARITY. 


Cork  and  sponge  are  rare  bodies. 
How  do  you  know  they  are  ? 
They  are  light,  and  can  be  cut  apart  more 
easily  than  iron  can. 


F  you  throw  a  hollow  In- 
dia  rubber  ball  upon  the 
floor,  will  it  lie  there  ? 

It  will  not;  it  will 
bound  up  into  the  air. 

What  makes  it  bound 


It  is  full  of  air ;  and  the  air  in 
it  makes  it  bound. 

Would  it  not  bound  up  if  it  was  filled  with 
something  besides  air  ? 

It  would,  but  not  near  so  high  as  it  does 
when  full  of  air. 

Will  you  tell  me  how  the  air  can  do  this  ? 

When  I  throw  down  the  ball,  the  side  that 


14  AIR.     ELASTICITY. 


touches  the  floor  is  flattened  or  bent  in,  and 
does  not  leave  as  much  room  for  the  air  in- 
side of  it. 

What  becomes  of  the  air  in  it,  then  ? 

The  particles  of  air  are  pressed  together 
so  closely  that  they  do  not  take  up  as  much 
room  as  they  did  before. 

What  presses  them  together  so  closely  ? 

The  striking  of  the  ball  against  the 
floor,  when  you  throw  the  ball  upon  the 
floor. 

How  long  will  the  air  in  the  ball  stay-in  so 
small  a  place  ? 

Not  a  moment. 

What  will  it  do  ? 

It  will  instantly  spring  back,  and  press  out 
the  flat  side  of  the  ball  as  round  as  it  was 
before. 

What  will  the  ball  do  then  ? 

It  will  bound  up  from  the  floor. 

What  is  the  springing  of  the  air  called  ? 

It  is  called  Elasticity. 


ELASTICITY.  15 


When  we  say  the  air  has  the  power  of 
springing  back,  what  do  we  mean  to  say  ? 

We  mean  to  say  that  the  air  is  elastic. 

What  other  bodies  are  elastic  ? 

Every  body  that  springs  back  to  its  first 
shape,  when  it  has  been  pressed  in  or  struck, 
is  an  elastic  body. 

Can  you  mention  some  bodies  that  are  elastic  ? 

Ivory,  wood,  and  many  other  hard  bodies 
are  elastic. 

What  bodies  are  not  elastic  ? 

Clay  and  wax  are  not  elastic. 

How  can  you  tell  whether  a  body  is  elastic  ? 

By  striking  it  against  another  body. 

What  will  it  do  if  it  is  elastic  ? 

It  will  bound  back,  without  seeming  to  be 
flattened  or  bent  inward. 

How  will  it  be  if  it  is  not  elastic  ? 

It  will  not  bound  back  again,  but  will  be 
flattened. 

How  do  you  know  that  the  air  we  breathe  is 
elastic  ? 


16  ELASTICITY.     THE  BENT  BOW. 


If  the  air  in  the  ball  is  elastic,  the  air  out 
of  the  ball  must  be  elastic  too. 

When  you  stretch  a  piece  of  India  rubber, 
what  makes  it  spring  back  as  soon  as  you  let 
it  go  ? 

Its  elasticity. 

If  you  pull  out  the  string  of  a  bow,  what 
will  happen  to  the  bow  ? 


It  will  bend. 

What  if  you  let  go  the  string  ? 
The  bow  will  straighten,  as  it  was  before. 
Why  will  it  straighten  ? 
Because  the  wood  of  which  the  bow  is  made 
is  elastic. 


ELASTIC  FLUIDS.  17 


Why  do  you  pull  the  string  hard  when  you 
fix  the  arrow  to  it  ? 

So  that  the  arrow  may  fly  the  farther. 

What  makes  the  arrow  fly  off  when  you  let 
go  the  string  ? 

The  bow  is  bent  when  I  put  on  the  arrow, 
and,  the  moment  I  let  go  the  string,  the  bow 
springs  back  so  quickly  that  it  straightens  the 
string  with  a  jerk,  and  the  arrow  is  sent  into 
the  air. 

Now  can  you  tell  me  what  it  is  that  makes 
the  arrow  fly  off  from  the  bow  ? 

It  is  the  elasticity  of  the  bow. 

You  said  the  air  is  a  fluid — then  are  fluids 
elastic  ? 

Some  fluids  are. 

What  fluids  are  elastic  ? 

Aeriform  fluids  are  called  elastic  fluids. 

2       • 


F  you  can  easily  bend  any 
body  you  hold  in  your 
hands,  as  you  can  a  piece 
of  steel  spring  or  a  wire, 
what  do  you  say  of  that 

body? 

Sa7  it  inflexible. 
What  is  the  meaning  of  FLEX- 
IBLE? 

Flexible  means  easily  bent. 
But  if,  instead  of  BENDING,  it  should  BREAK 
what  kind  of  a  body  should  you  call  it 
I  should  call  it  brittle. 
What  do  you  mean  by  a  BRITTLE  body  ? 
I  mean  a  body  that  easily  breaks. 


FLEXIBILITY.     MALLEABILITY.  19 

Mention  some  BRITTLE  bodies. 

Glass  and  china  are  brittle,  ice  is  brittle, 
stones  are  brittle,  and  so  are  some  metals. 

What  bodies  are  flexible  ? 

Tin,  lead,  India  rubber,  thin  plates  of  most 
metals,  and  wires. 

Could  any  one,  hammer  out,  or  roll  out,  gold 
and  silver  into  thin  plates  ? 

He  could,  with  heavy  hammers  or  machines. 

When  any  metal  can  be  hammered  out  thin- 
ner, without  breaking,  what  do  we  call  it  ? 

We  call  it  malleable  or  hammer-able. 

Is  CHALK  malleable  ? 

It  is  not. 

How  do  you  know  ? 

If  I  strike  it  with  a  hammer,  it  breaks  in 
pieces,  instead  of  spreading  out  thin. 

Then  what  do  you  say  of  chalk  ? 

I  say  it  is  brittle. 

How  thin  can  gold  and  silver  be  rolled  out,  or 
hammered  ? 

Till  they  are  thinner  than  paper. 


20  MALLEABILITY.     TENACITY. 


What  are  they  then  called  ? 

Gold-leaf  and  silver-leaf. 

How  thin  can  gold-leaf  be  made  ? 

So  thin  that  three  hundred  and  sixty  thou- 
sand leaves  of  it,  when  all  laid  together  in  a 
pile,  would  be  only  an  inch  thick. 

Of  what  use  is  such  thin  gold-leaf? 

It  is  used  to  cover  looking-glass  and  pic- 
ture frames,  and  to  put  upon  wood,  or  leather, 
or  paper. 

When  any  thing  is  covered  with  gold-leaf, 
what  do  we  call  it  ? 

We  call  it  gilt  or  gilded  wood  or  paper. 

When  a  metal  can  be  stretched  out,  like  a 
wire,  to  a  great  length,  without  breaking,  what 
is  it  that  keeps  it  from  breaking  ? 

Its  tenacity. 

What  is  the  meaning  ef  TENACITY  ? 

Tenacity  means  its  power  of  holding  to- 
gether. 

Then  has  WIRE  great  tenacity  ? 

It  has. 


SUSPENSION. 


21 


Can  you  tell  about  any  tiling  that  shows  the 
wonderful  tenacity  of  IRON-WIRE  ? 

Very  strong  bridges  are  made  across  some 
rivers,  for  the  heavy  locomotive  and  cars  to 
go  safely  across,  and  yet  these  bridges  hang 
on  wires  of  iron. 


What  is  the  name  of  such  bridges  ? 
They  are  called  suspension  bridges. 
What  is  the  meaning  of  SUSPENSION  ? 
Hanging;     for     they     hang     upon 
wires. 


the 


22  SUSPENSION. 


How  are  the  wires  fastened  each  side  of  the 
river  ? 

A  strong  tower  is  built  on  each  bank  of 
the  river,  and  the  long,  large  wires  pass 
over  the  towers,  and  are  fastened  firmly  into 
the  ground  beyond. 


fmirt|. 


HEN  you  say  a  body  is 
MOVING,  what  do  you 
mean  ? 

I  mean  that  the  body 
is  changing  its  place. 

Then    what    is     the 
meaning  of  the  word  MOTION  ? 

Motion  means  change  of  place. 
When  your  ball  moves  along  the  floor,  what 
PUTS  it  in  motion  ? 
My  hand. 

When  the  arrow  flew  through  the  air,  what 
put  it  in  motion  ? 

The  springing  of  the  bow  made  it  fly  off 
Then  what  puts  bodies  in  motion  ? 
The  power   of   the    body  that  strikes,  or 
pushes,  or  draws  them,  puts  them  in  motion. 


24:  FORCE.     ATTRACTION. 


What  is  this  power  called  ? 

It  is  called  force. 

What  put  the  arrow  in  motion  ? 

The  force  of  the  elasticity  of  the  bow. 

How  do  you  know  ? 

If  the  bow  had  not  been  elastic,  the  arrow 
would  never  have  left  the  string. 

What  can  stop  the  motion  of  a  body? 

The  power  or  force  of  something  else 
can  make  it  stop. 

What  makes  an  arrow  stop  moving,  after  it 
has  been  shot  into  the  air  ? 

If  it  falls  to  the  ground,  it  is  the  force  of 
the  attraction  of  gravitation  that  brings  it 
down. 

If  it  goes  into  a  tree  or  a  board,  what  force 
stops  it  then  ? 

The  force  of  the  cohesive  attraction  of  the 
particles  of  wood  stops  it 

How  does  the  cohesive  attraction  stop  it  ? 

It  keeps  the  particles  of  wood  so  closely 
together  that  the  arrow  can  not  separate  them. 


MOTION.  25 


When  the  wood  will  not  permit  the  arrow 
to  go  through  it,  what  do  we  say  the  wood 
does  ? 

We  say  the  wood  resists  the  arrow. 

Which  is  it  that  resists  the  arrow,  the 
particles  of  wood,  or  the  cohesive  attraction 
that  draws  the  particles  together  ? 

It  is  the  attraction  of  cohesion. 

How  do  you  know  ? 

If  the  cohesion  could  be  taken  from  the 
wood,  the  arrow  would  pass  through  it. 

When  you  throw  a  ball  into  the  air,  will  it 
move  all  the  time  as  fast  as  it  did  when  you 
first  threw  it? 

It  will  not,  but  will  go  slower  and  slower, 
till  it  falls. 

When  the  motion  of  a  lody  becomes  slower 
and  slower,  what  do  we  call  such  motion  ? 

We  call  it  retarded  motion. 

What  is  the  meaning  of  RETARDED  ? 

Any  thing  is  retarded  that  goes  slower  and 
slower. 


26  MOTION. 


If  you  were  running,  how  could  you  RETARD 
your  motion? 

By  beginning  to  walk. 

If  you  were  walking,  and  should  begin  to 
run,  and  should,  continue  to  run  faster  and 
faster,  what  kind  of  motion  would  that  be  ? 

It  would  be  accelerated  motion. 

What  do  you  mean  by  ACCELERATED  motion? 

Quickened  motion. 

If  you  were  walking,  and  should  not  go  any 
faster  or  any  slower, *  what  motion  would  that 
be? 

It  would  be  uniform  motion. 

What  is  meant  by  UNIFORM  motion  ? 

Motion  that  is  always  alike,  never  slower 
or  faster. 

Mention  some  body  that  always  moves  alike. 

The  minute-hand  of  a  watch,  and  all  the 
wheels  in  a  watch,  move  just  as  fast  at  one 
time  as  they  do  at  another. 

Then  what  is  the  motion  of  a  watch  ? 

It  is  uniform  motion. 


MOTION. 


27 


When  a  ball  is  falling  to  the  ground,  what 
is  its  motion  ? 

It  is  accelerated  motion. 

Why  is  it  accelerated  1 

Because  the  attraction  of  trie  earth  draws 
it  more  and  more,  the  nearer  it  comes  to  the 
earth,  and  this  makes  the  ball  fall  faster  and 
faster. 


When    you  throw   up  a  loll,  what  is   its 
motion  ? 

It  is  retarded  motion. 


28  MOTION. 


Why  is  it  retarded  motion  ? 

Because  the  attraction  of  the  earth  draws 
it  down  when  my  hand  sends  it  up,  and  this 
makes  the  ball  go  slower  and  slower,  till  it 
finally  falls  to  the  ground. 

How  many  kinds  of  motion  have  you  men- 
tioned ? 

Three. 

What  are  they  called  ? 

Retarded  motion,  accelerated  motion  and 
uniform  motion. 

How  does  a  body  move  when  its  motion  is 
retarded  ? 

Slower  and  slower. 

How  when  its  motion  is  accelerated  ? 

Faster  and  faster. 

How  when  its  motion  is  uniform  ? 

Neither  faster  nor  slower,  but  always 
alike. 

When  you  say  a  ball  ASCENDS,  what  do  you 
mean  ? 

I  mean  that  the  ball  goes  up,  or  rises. 


MOTION.  29 


When  a  body  DESCENDS,  what  does  it  do  ? 

It  goes  down,  or  falls 

What  kind  of  motion  does  a  "body  have  by 
being  thrown  upward  ? 

Retarded  motion;  because  it  rises  slower 
and  slower. 

What  is  the  motion  of  this  body  when  it 
descends  ? 

Accelerated  motion;  because  it  falls  quicker 
and  quicker. 

What  is  the  motion  of  water  when  it  is  fall- 
ing in  a  cataract  ? 

It  is  accelerated  motion. 

Which  has  the  greatest  weight,  a  cannon  ball 
or  a  bullet  ? 

A  cannon  ball. 

If  you  could  throw  a  cannon  ball  against  a 
thin  board,  would  it  go  through  the  board 

It  would  not. 

If  a  bullet  should  be  shot  out  of  a  gun, 
would  it  go  through  the  board  ? 

It  would. 


30  STRENGTH.     WEIGHT.     VELOCITY. 


Why  would  the  bullet  go  through,  when  the 
cannon-ball,  which  is  much  heavier,  would  not  ? 

Because  the  bullet  goes  so  much  faster 
than  the  ball. 

What  is  swift  motion  called  ? 

Velocity. 

Then  why  will  the  bullet  go  through  the 
board,  when  the  ball  will  not  ? 

Because  the  weight  and  velocity  of  the 
bullet  together,  is  greater  than  the  weight  and 
velocity  of  the  ball,  when  put  together. 

When  weight  and  velocity  are  put  together, 
what  is  the  whole  called  ? 

The  momentum  of  the  body. 

Which  momentum  is  greatest,  then,  that  of  a 
cannon-ball  thrown  by  the  hand,  or  that  of  a 
bullet  fired  from  a  gun  ? 

That  of  the  bullet. 

How  could  you  increase  the  momentum  of 
the  cannon-ball  ? 

By  firing  it  from  a  cannon. 


HEN  you  throw  a  ball 
against  the  wall,  what 
becomes  of  the  ball  ? 

It  will  bound  back, 
as  if  the  wall  threw  it 
back  to  me. 

What  is  its  motion  from  the 
wall  bach  to  you  called  ? 
It  is  called  reflected  motion. 
What  is  meant  by  REFLECTED  motion  ? 
The  motion  made  by  throwing  back  any 
thing. 

What  is  the  meaning  of  the  word  REFLECT  ? 
It  means  to  throw  back  again. 
Then,  when  I  say  a  body  is  reflected,  what 
do  I  mean  ? 


32  COMPOUND  MOTION. 


You  mean  that  the  body  is  thrown  back 
again. 

If  I  should  strike  a  ball  to  make  it  go  one 
way,  and  you  should  strike  it  at  the  same  time 
to  make  it  go  another  way,  what  would  its 
motion  be  called  ? 

It  would  be  called  compound  motion. 

Why  would  it  be  called  COMPOUND  motion  ? 

Because  it  would  be  two  motions  put 
together. 

What  two  motions  would  it  be  ? 

The  motion  which  your  hand  gave  it,  and 
the  motion  which  my  hand  gave  it  at  the 
same  time. 

Which  way  would  the  ~ball  move  if  we  struck 
it  together  1 

It  would  not  go  the  way  your  hand  sent  it, 
nor  the  way  my  hand  sent  it,  but  it  would 
move  between  those  ways. 

In  what  kind  of  a  LINE  does  the  ball  move 
after  being  struck  by  both  our  hands  ? 

In  a  straight  line. 


RECTILINEAR  MOTION.  33 

What  is  the  motion  of  the  ball  called  ? 
It  is  called  rectilinear  motion. 
What  is  the  meaning  of  RECTI-LINEAR  ? 
Straight  line. 

Here  is  a  diagram  which  will  show  you 
how  the  ball  would  move. 


When  you  hold  a  string  that  is  tied  to  a  ball, 
and  swing  the  ball  round,  what  is  the  motion  of 
the  ball? 

It  is  circular  motion. 

Why  is  it  called  CIRCULAR  motion  ? 

Because  the  ball  moves  round  in  a  circle. 

What  is  the  motion  of  the  earth  around  the 
sun  called  ? 

It  is  called  circular  motion. 

3 


34  CIRCULAR  MOTION. 

Why? 

Because  tlie  earth  moves  in  a  circle  around 
the  sun. 

Here  is  a  diagram  which  shows  you  what 
circular  motion  is. 


If  you  throw  your  ball  forward,  will  it  fall 
down  -to  the  ground  in  a  straight  line  ? 

No ;  it  will  make  a  curved  line,  like  the 
diagram. 


CURVILINEAR  MOTION.  35 


What  then  is  the  motion  of  the  ball  called  ? 

It  is  called  curvilinear  motion. 

What  is  the  meaning  of  CURVILINEAR? 

Curved  line. 

Then  what  is  curvilinear  motion  ? 

Motion  in  a  curved  line. 

What  makes  the  ball  move  in  a  curved 
line  ? 

My  hand  sends  it  straight  forward,  and 
the  attraction  of  the  earth  draws  it  straight 
down. 

Then  which  way  will  the  ball  move  ? 

It  can  not  go  either  way,  but  goes  between. 

Then  is  curvilinear  motion  compound  motion? 

It  is. 

Why  ? 

Because  it  is  the  motion  made  by  my 
hand  and  the  attraction  of  gravitation  to- 
gether. 

Is  circular  motion  compound  motion  also  1 

It  is. 

Why  ? 


36  MOTION.     FORCE. 


Because  it  is  made  by  throwing-  the  ball 
into  the  air,  while  at  the  same  time  you  keep 
it  from  going  off  by  holding  the  string. 

Why  is  one  kind  of  compound  motion  REC- 
TILINEAR and  another  CURVILINEAR  ? 

When  both  of  the  hands  or  forces  are 
taken  away  as  soon  as  they  have  struck  the 
ball,  it  will  move  in  a  straight  line. 

Then  what  motion  will  the  ball  have  ? 

Rectilinear  motion. 

How  will  it  be,  when  one  force  continues  to 
move  the  ball  after  the.  oilier  is  removed  ? 

The  motion  will  be  in  a  curved  line,  or 
curvilinear. 

When  you  throw  a  ball  straight  forward, 
what  force  continues  to  move  the  ball  after  it 
leaves  your  hand  ? 

The  attraction  of  the  earth  draws  it  to  the 
ground  in  a  curved  line. 

How  is  the  circular  motion  of  the  earth  com- 
pound motion  too  ? 

The  centrifugal  force  makes  it  go  from  the 


MOTION.     FORCE. 


37 


center,  and  the  centripetal  force  draws  it  to 
the  center. 

To  what  center  ? 

The  sun ;  because  the  earth  moves  round 
the  sun. 


tart  !j> 


•p^  HEN    a  pendulum   to    a 
clock  swings  backward 
and    forward,   does   it 
move  in  a  straight  line  ? 
It  does  not ;  the  line 
is   curved,  like  a  part 
of  a  circle. 

Why  does  it  not  swing  quite 
around  the  place  where  it  is  fastened,  just  as 
the  ball  does  when  you  whirl  it  round  your 
hand.  ? 

The  attraction  of  gravitation  draws  the 
pendulum  down  toward  the  ground  when  it 
begins  to  go  up. 

Then  why  does  not  the  pendulum  stop,  in- 
stead of  going  up  the  other  side  ? 


ATTRACTION  OF  GRAVITATION. 


39 


Because  it  goes  down  so  fast  that  it  can 
not  stop  in  an  instant. 


What  is  this  like  ? 

Like  a  boy  sliding  down  hill. 


40 


ATTRACTION  OF  GRAVITATION. 


How  does  he  go  ? 

He  goes  so  fast  down  the  hill,  that  when 
he  gets  to  the  bottom  he  can  not  stop,  but 
goes  part  way  up  the  next  before  the  sled 
stands  still. 


How  would  it  be,  if  he  should  slide  down  the 
second  hill  ? 

He  would  go  part  of  the  way  again  up  the 
first. 

And  how  is  this  like  a  pendulum  ? 

When  my  hand  draws  aside  the  pendulum, 
and  then  lets  it  go  again,  the  attraction  of 
gravitation  draws  it  down  as  far  as  it  can ; 


ATTRACTION  OP  GRAVITATION.  41 


and,  because  it  can  not  stop  itself,  it  will  go 
up  the  other  side. 

What  will  it  do  then  ? 

The  earth  will  draw  it  down  again  so  fast, 
as  to  send  it  up  the  side  from  which  it 
started. 

What  is  a  favorite  amusement  of  the  Rus- 
sians ? 

Sliding  down  ice-hills. 

How  is  an  ice-hill  made  ? 

It  is  made  of  wood,  covered  with  water 
frozen  to  ice  ;  it  has  three  ascents,  one  above 
another,  with  a  little  valley  between  each 
ascent. 

How  do  they  slide  down  this  ice-hill  ? 

At  the  top  of  the  hill  they  seat  themselves 
on  a  sled  made  for  the  purpose,  and  slide 
down  the  first  ascent  very  swiftly. 

Will  the  sled  stop  there  ? 

It  will  not. 

Why  will  it  not  ? 

Because  it  came  down  so  fast,  that  it  will 


42  ATTRACTION  OF  GRAVITATION. 


slide  acrovss  the  little  valley  and  up  to  the  top 
of  the  next  ascent ;  and  then  down  that,  in 
the  same  manner. 

What  keeps  a  pendulum  of  a  dock  in  motion 
all  the  time? 

The  wheels  that  are  inside  of  the  clock. 

What  makes  the  wheels  move  ? 

The  weights  that  draw  the  strings  that  are 
fastened  to  the  wheels. 

How  long  will  the  pendulum  swing  before  it 
stops  ? 

Till  the  wheels  stop  moving. 

How  long  will. the  wheels  move  around? 

Till  the  weights  reach  the  bottom  of  the 
clock. 

How  can  they  be  put  in  motion  again  ? 

By  winding  up  the  strings  that  fasten  the 
weights  to  the  wheels. 

What  makes  the  weights  go  down  to  the  bot- 
tom of  the  clock  ? 

The  attraction  of  gravitation. 

What  is  the  attraction  of  gravitation  ? 


ATTRACTION  OF  GRAVITATION.  43 


The  attraction  of  the  earth. 

Then,  when  a  clock  goes,  what  does 
the  attraction  of  gravitation  do  to  make  it 
go? 

It  keeps  the  wheels  in  motion,  and  thus 
helps  to  keep  the  pendulum  swinging. 

How  fast  does  a  pendulum  commonly  swing 
backward  and  forward  ? 

Once  in  every  second,  which  would  make 
sixty  times  every  minute. 

Can  any  thing  be  made  to  move  forever  with- 
out stopping  ? 

No,  nothing. 

Has  any  one  ever  tried  to  make  a  body  move 
forever  ? 

Yes ;  many  have  tried,  but  they  could  not 
do  it. 

If  a  body  should  move  forever,  what  would 
its  motion  be  called  ? 

Perpetual  motion. 

What  is  the  meaning  of  PERPETUAL  ? 

Perpetual  means  never-ending. 


44  PERPETUAL  MOTION". 


Then  what  is  perpetual  motion  ? 

Never-ending  motion. 

How  many  motions  have  you  learned 
about  ? 

Eight. 

What  is  the  first? 

Retarded  motion,  or  motion  that  becomes 
slower  and  slower,  as  if  a  boy  stopped  run- 
ning and  began  to  walk. 

What  is  the  second  ? 

Accelerated  motion,  or  motion  that  becomes 
faster  and  faster,  as  if  he  began  to  run 


again. 


The  third? 

Uniform  motion,  or  motion  that  is  always 
alike,  like  a  clock. 

The  fourth? 

Reflected  motion,  or  moving  back  again 
like  a  ball  bounding  back  from  a  wall. 

The  fifth? 

Compound  motion,  or  two  motions  together. 

The  sixth? 


MOTION.  45 


Circular  motion,  or  motion  in  a  circle,  like 
swinging  a  ball  tied  to  a  string. 

The  seventh  ? 

Curvilinear  motion,  or  motion  in  a  curved 
line. 

The  eighth? 

Perpetual  motion,  or  motion  that  will  never 
stop. 


ow    6?o   children  play  at 
SEE-SAW? 

They  take  a  plank  of 
wood,  and  lay  it  across 
a  block  or  a  fence,  and 
then  one  sits    on   each 
end,   and    they    swing   up   and 
down  the  see-saw. 
What  is  a  plank  sometimes  called  ? 
It  is  called  a  lever. 
What  is  a  lever  ? 

A  rod  or  plank  that  will  not  bend  easily  is 
a  lever. 

What  is  the  block  that  it  rests  upon  called  ? 
It  is  called  a  fulcrum. 
What  is  a  fulcrum  ? 


THE  LEVER. 


47 


That  which  the  lever  or  plank  stands  upon, 
when  its  ends  are  moving^up  and  down. 


If  the  plank  were  laid  across  a  fence,  when 
you  play  at  see-saw,  what  would  be  its  ful- 
crum ? 

That  part  of  the  fence  that  it  lies  across. 

What  are  the  parts  of  the  lever  each  side  of 
the  fulcrum  sometimes  called? 

They  are  called  arms  of  the  lever. 

Then,  if  you  were  playing  at  see-saw,  where 
would  the  arms  of  the  lever  be  ? 

I  should  sit  on  one  arm  of  the  lever,  and 
my  companion  would  sit  on  the  other  arm. 


48  THE  LEVER. 


If  you  are  just  as  heavy  as  your  companion, 
where  must  the  block,  or  the  fulcrum  of  the 
plank,  be  placed? 

Exactly  in  the  middle,  so  that  one  .arm  may 
be  just  as  long  as  the  other. 

Then,  if  you  sat  still  upon  the  plank,  would 
it  move  up  and  down? 

Each  arm  would  exactly  balance  the  other, 
and  it  would  stand  still. 

When  do  bodies  balance  each  other  ? 

When  one  is  just  as  heavy  as  the  other. 

If  your  companion  is  twice  as  heavy  as  you 
are,  how  must  the  plank  be  placed  on  the  ful- 
crum ? 

So  that  the  arm  on  which  I  sit  may  be 
almost  twice  as  long  as  hers. 

Where  would  the  fulcrum  be,  then? 

Near  my  companion. 

What  POWER  sets  the  lever  in  motion  up  and 
down  ? 

We  are  the  power ;  because  I  strike  my 
feet  on  the  ground,  so  as  to  send  myself  up, 


THE  LEVER.  49 


and  that  makes  my  companion  go  down ;  and 
then  she  does  the  same,  and  goes  up  while  I 
go  down. 

If  a  stone  much  heavier  than  yourself  should 
be  placed  on  one  arm  of  the  lever,  how  could 
you  raise  up  the  stone  ? 

By  putting  the  fulcrum  so  near  it,  that  the 
arm  on  which  the  stone  lies  would  be  very 
short,  and  the  other  very  long. 

Would  you  have  to  use  much  strength  to  raise 
it,  then  ? 

I  should  not,  if  the  long  arm  was  very 
heavy. 

Why  would  you  not  ? 

Because  the  long  arm  would  be  so  heavy, 
that  it  would  almost  raise  the  stone  on  the 
other  arm  of  itself. 

Then  what  is  the  use  of  the  lever  ? 

It  assists  us  in  raising  large  and  heavy 
bodies. 

In  raising  the  stone,  what  was  the  power  ? 

My  hand. 


50  THE  LEVER, 


What  was  the  weight  ? 
The  stone. 


What  was  the  fulcrum  ? 

The  block  upon  which  the  lever  rested. 

Where  was  the  fulcrum  placed  ? 

Between  the  power  and  the  weight,  or  be- 
tween the  hand  and  the  stone. 

Is  a  pair  of  scissors  like  a  lever  ? 

Yes  ;   it  is  two  levers,  fastened  together. 

Do  both  levers  move  the  same  way  ? 

No ;  when  one  moves  up,  the  other  goes 
down,  till  they  meet  together. 

What  is  the  fulcrum  of  each  lever  ? 

They  both  have  the  same  fulcrum. 


THE  LEVER.  51 


What  is  it? 

Each  lies  across  the  other,  and  they  are 
fastened  together,  where  they  cross,  by  a 
small  rivet  or  screw  that  goes  through  them. 


Then  what  is   the  fulcrum    of  the    scis- 


sors ? 


The  rivet  that  fastens  the  scissors  together. 

What  is  the  power  that  moves  these  levers  ? 

My  hand. 

What  is  the  weight  ? 

If  I    am  cutting  paper,  the  paper  is  the 
weight. 

Will    you  tell  me   why   the  paper  is   the 
weight  ? 

-  Because,  when  I  am  cutting  it,  I  lift  up  the 
paper  with  the  lever  which  my  thumb  draws 


52  THE  LEVER. 


down,  and  I  press  clown  the  paper  with  the 
lever  which  my  fingers  draw  up. 

How  will  this  cut  the  paper  ? 

The  levers  are  screwed  so  tight  to  each 
other,  that  when  they  come  together  there  is 
no  room  for  the  paper  between  them. 

What  becomes  of  the  paper,  then  ? 

One  part  of  the  paper  remains  on  one  side 
of  the  scissors,  and  the  other  part  is  on  the 
other  side,  and  the  scissors  are  between 
them. 

Then  what  have  the  scissors  done  to  the 
paper  ? 

They  have  divided  it. 

Are  the  scissors  the  same  kiftd  of  lever  as 
the  see-saw  ? 

They  are. 

How  do  you  know  they  are  ? 

Because,  in  them  both,  the  power  is  at  one 
end,  the  weight  at  the  other,  and  the  fulcrum 
between. 


HEN  a  merchant  weighs 
out  a  pound  of  sugar, 
how  does  he  do  it  ? 

He  takes   a  pair  of 
scales,  or  balances,  like 
those    in  this    picture, 
puts  a  piece  of  lead,  that 
weighs  exactly  a   pound,  into 
one  of  the  scales. 


54  THE  LEVER. 


Then  what  does  he  do  with  the  sugar  ? 

He  puts  just  as  much  sugar  into  the 
other  scale  as  will  lift  up  the  weight  in  the 
first  scale. 

How  can  he  tell  when  he  has  put  in  a  pound 
of  sugar ? 

When  one  scale  is  just  as  heavy  as  the 
other,  then  the  sugar  is  weighed  right. 

Are  these  scales  like  a  lever  ? 

Yes,  they  are  a  lever. 

Which  is  the  fulcrum  ? 

The  place  where  they  are  hung  up  is 
the  fulcrum. 

What  is  the  weight  ? 

The  lead  in  one  scale. 

What  is  the  power  that  raises  the  lead  ? 

The  sugar  in  the  other  scale. 

Then,  is  not  the  lever  very  useful  ? 

It  is ;  it  would  be  very  difficult  for  us  to 
do  many  things  without  the  lever. 


HEN  you  open  a  door, 
which  is  the  weight  that 
you  move  1 

The   door  is    the 
weight. 

What  is  the  fulcrum? 
The  hinges  are  the  fulcrum. 
What  is  the  power  ? 
My  hand. 

Is  the  door  such  a  kind  of  lever  as  the  see- 
saw? 
It  is  not 
Why  is  it  not  ? 

Because  the  weight  is  between  the  power 
and  the  fulcrum. 


56 


THE  LEVER. 


How  is  it  with  the  see- saw  ? 
The  fulcrum  is  between  the  power  and  the 
weight. 


Is  there  any  other  kind  of  lever  ? 

There  is  one  more. 

What  is  it  ? 

It  is  a  lever  which  has  the  power  between 
the  weight  and  the  fulcrum 

Have  you  ever  seen  such  a  lever  ? 

Yes ;  when  I  have  seen  a  man  raising  a 
ladder  against  the  wall. 


THE  LEVEE.  57 


What  was  the  fulcrum  ? 
The  ground,  on  which  the  bottom  of  the 
ladder  rests. 


What  the  weight  ? 

The  ladder.  I 

What  was  the  power  ? 

The  strength  of  his  hands. 

Then  how  many  kinds  of  levers  are 
there  ? 

Three  kinds. 

What  is  the  first  ? 

One  where  the  fulcrum  is  between  the 
power  and  the  weight — as  the  see-saw. 


58  WHEEL  AND  AXLE. 


What  the  second  ? 

One  where  the  weight  is  between  the 
power  and  the  fulcrum — as  the  door. 

What  the  third  ? 

Where  the  power  is  between  the  fulcrum 
and  the  weight — as  a  man  raising  a  ladder. 

What  is  another  means  of  raising  weights 
besides  the  lever  ? 

The  wheel  and  axle. 

What  is  the  shape  of  a  wheel  ? 

It  is  round,  like  a  hoop,  with  sticks,  called 
spokes,  going  from  the  outside  to  the 
center. 


What  is  the  axle  of  a  wheel  ? 
The  place  where  the  spokes  are  fastened 
in  the  center  of  the  wheel. 


WHEEL  AND  AXLE.  59 


Here  is  a  picture  of  a  wheel  and  axle. 


What  is  the  use  of  a  wheel  and  axle  ? 

It  is  used  to  raise  weights. 

Have  you  ever  seen  a  wheel  and  axle  used  in 
raising  a  weight  ? 

Some  wells  have  a  wheel  and  axle  to  raise 
up  the  bucket  of  water  out  of  them. 

How  is  it  done  ? 

The  rope  or  chain  on  which  the  bucket 
hangs  is  fastened  to  the  axle,  and  so,  when 


50  "WHEEL  AND  AXLE. 


the  wheel  turns  around,  the  .rope  winds 
around  the  axle  till  the  bucket  comes  up. 

Can  you  tell  how  a  wheel  and  axle  is  like  a 
lever  1 

The  spokes  are  the  long  arms  of  the  lever, 
and  the  parts  of  them  that  go  into  the  axle 
are  the  short  arms. 


Cm  tip 


HY  will  a  ball  roll  down 
^    upon   the  floor,  if  you 
place  it  upon  a  desk  ? 

Because  the  desk  is 
not  level,  like  a  table, 
but  inclines  downward. 
What  may  a  desk  then  be  called? 
An  inclined  plane. 
What  is  a  plane  ? 
A  smooth  surface. 
What  is  an  INCLINED  PLANE  ? 
A  smooth  surface,  that  slopes  or  inclines 
downward. 

What  is  the  use  of  an  inclined  plane  ? 
It  is  used  to  raise  weights. 
How  is  a  weight  raised  easier  by  an  inclined 
plane  than  without  it  ? 


62 


INCLINED  PLANE. 


If  we  put  one  end  of  a  long  board  upon  a 
wagon,  and  let  the  other  rest  upon  the  ground, 
and  roll  a  barrel  up  the  board  into  the  wagon, 
we  shall  find  it  much  easier  than  it  would  be 
to  lift  it  straight  up  from  the  ground  into  the 
wagon. 

Here  is  a  picture  of  an  inclined  plane,  with 
a  weight  rolling  up  upon  it. 


What  is  the  shape  of  the  blade  of  a  knife? 
It  is  like  two  inclined  planes,  put  together. 
What  would  the  blade  of  a  knife  be  called 
in  Philosophy  1 

It  would  be  called  a  wedge. 


WEDGE. 


68 


What  is  a  WEDGE  ? 

It  is  like  two  inclined  planes,  put  together, 
so  as  to  have  a  sharp  edge  on  one  side,  where 
they  meet. 


Here  is  a  picture  of  a  wedge  in  a  log. 


Of  what  use  is  a  wedge  ? 

A  wedge  is  used  for  cutting  or  dividing 


things. 


64  SCREW. 


Mention  the  names  of  some  wedges. 

A  knife  is  a  wedge,  and  so  is  an  axe, 
and  almost  all  cutting  instruments  are 
wedges. 

Have  you  ever  seen  a  screw  ? 

I  have,  very  often. 

Where  have  you  seen  them  ?• 

A  pair  of  scissors  is  fastened  together  with 
a  little  screw,  and  hinges  and  locks  are  fas- 
tened upon  doors  with  screws. 

Why  are  not  nails  as  good  as  screws  to  fasten 
them  with? 

A  nail  might  be  pulled  out ;  but  the  sharp 
edge,  that  rises  and  winds  around  the  screw, 
keeps  it  in  tight,  just  where  it  is  fastened. 


PULLEY. 


65 


What  is  a  screw  like  ? 

It  is  much  like  a  round  nail,  with  a  sharp 
wedge  wound  around  it. 

Of  what  use  is  the  sharp  edge  or  wedge 
around  the  screw  ? 

It  cuts  the  wood  where  it  goes  in,  while  we 
are  turning  it,  and  holds  the  screw  in  its  place. 

Here  is  the  picture  of  a  screw. 


What  is  a  PULLEY  ? 

A  pulley  is  a  little  wheel  and  axle,  with  its 
edge  hollowed  out,  so  as  to  make  a  place  for  a 
cord  to  wind  around  it. 

5 


66 


PULLEY. 


Here  is  one,  with  a  cord  upon  it. 


Of  what  use  is  a  pulley  ? 

Weights  are  raised  by  means  of  pulleys, 
and  removed  to  other  places. 

How  do  they  help  people  to  raise  weights  1 

The  weight  is  fastened  to  one  end  of  the 
cord,  and  a  person  can  raise  the  weight  by 
pulling  down  the  other  end  of  the  cord. 

How  are  buckets  of  water  sometimes  raised 
out  of  a  well  ? 

A  rope  is  put  over  a  large  pulley,  that  is 
fixed  above  the  well,  and  a  bucket  is  fastened 
to  each  end  of  this  rope. 


PULLEY. 


67 


When  one  bucket  is  filled  in  the  well,  how  is 
it  easily  brought  up  ? 

By  drawing  down  the  other  bucket. 

Why  does  it  require  so  little  strength  to  do 
this  ? 

Because  the  weight  of  the  empty  bucket 
helps  to  draw  down  that  end  of  the  rope,  and 
raise  the  full  bucket  at  the  other  end. 


How  many  kinds  of  pulleys  are  there  ? 
Two ;    the  fixed  pulley  and  the  moveable 
pulley. 


68 


PULLEY. 


What  is  afxed  pulley  ? 

A  pulley  that  turns  round,  but  remains 
fixed  in  the  same  place. 

What  is  a  moveable  pulley  ? 

A  pulley  that  is  constantly  moving  from 
some  place,  as  it  turns  round. 


ess  ait 


w 


HAT  are  the  lever,  wheel, 
pulley,  inclined  plane, 
wedge,  and  screw  called 
in  Philosophy  ? 

They  are  called  me- 
chanical powers, 
hat  do  you  mean  by  mechan- 
ical powers  ? 
The  power  of  machines  or  instruments. 
Of  what  use  are  the  mechanical  powers  ? 
They  help  us  to  raise  and  move  very  large 
weights,  and  to  divide   and  cut  hard  bodies 
into  any  shape  we  please. 

Can  you  mention  some  useful  machines  ? 
Clocks  and  watches,  locomotives  and  steam 
engines,  are  useful  machines. 


70 


MOVING  POWER. 


Of  what  use  are  steamboats  ? 

They  carry  very  heavy  loads  of  goods  and 
people  across  the  water,  much  faster  than 
vessels  can. ' 

How  can  they  do  this  ? 

By  means  of  the  machinery  in  them. 

What  keeps  the  machinery  in  motion  ? 

The  power  of  the  steam. 


MOVING  POWER.  71 


How  can  the  cars  on  railroads  move  so 
very  rapidly  ? 

It  is  by  means  of  the  power  in  the  loco- 
motive engine,  that  draws  them. 

Does  steam  keep  these  machines  in  motion  ? 

It  does. 

What  do  you  mean  by  MACHINE  or  MA- 
CHINERY? 

When  several  instruments  or  mechanical 
powers  are  put  together,  we  call  the  whole  a 
machine  or  machinery. 

What  did  you  say  kept  the  machinery  of 
steamboats  in  motion  ? 


The  power  of  the  steam. 


I 

72  MOVING  POWER, 


What  is  steam  called  when  it  moves  ma- 
chinery ? 

It  is  called  a  moving  power. 

Then  what  is  the  moving  power  of  steam- 
boats ? 

Steam. 

What  is  the  moving  power  of  railroad  cars  ? 

Steam. 

What  is  the  moving  power  of  a  clock  ? 

Gravitation. 

How  do  you  know  ? 

It  is  gravitation  which  draws  down  the 
weights,  that  turn  the  wheels,  and  keep  the 
clock  going. 

In  mills  and  manufactories  upon  the  banks 
of  rivers,  what  is  the  moving  power  ? 

The  water. 

How  do  you  know  ? 

It  is  the  water  running  upon  the  great 
wheels  that  keeps  them  turning;  because, 
when  the  stream  is  very  low,  or  almost  dry, 
the  wheels  stop  turning. 


MOVING  POWER.  73 

Is  water  the  moving  power  of  all  mills? 
No ;  the  moving  power  of  some  mills  is 
wind. 


What  are  such  mills  called  ? 

Windmills. 

When  animals  or  men  move  machines,  what 
do  we  say  the  moving  power  of  such  machines 
or  instruments  is  ? 

Animal  strength,  or  the  strength  of  men 
and  animals,  is  their  moving  power. 

Who  has  provided  the  moving  powers  of  all 
machines  ? 

The  Creator  of  the  world. 


74  MOVING  POWER. 


What  good  have  they  done  for  man? 

They  save  him  from  much  very  hard 
labor. 

How  do  they  do  this  ? 

With  a  machine,  one  man  can  do  the  work 
that  would  require  all  the  strength  of  many 
men  to  do,  without  it 

Can  you  mention  one  example  ? 

In  cotton  factories,  where  cotton  cloth  is 
made,  they  have  machines  to  card,  and  spin, 
and  weave ;  so  that  a  very  few  persons  can 
make  hundreds  or  thousands  of  yards  of  cloth 
in  a  day,  from  cotton  that  is  brought  in,  the 
same  morning. 

Can  you  mention  anotlwr  example  ? 


On  railroads,  a  little  steam-engine  can  draw 


CURIOUS  CLOCKS.  75 


a  great  many  heavily  loaded  cars  thirty 
miles  in  one  hour. 

Who  teaches  man  how  to  save  his  labor  by 
contriving  these  machines  ? 

Our  Creator 

How  does  he  teach  us  ? 

He  made  the  wood  and  iron  of  which  ma- 
chines are  made;  and  the  wind,  and  water, 
and  strength,  that  moves  them ;  and  He 
teaches  the  mind  in  us  to  think  and  contrive 
how  to  use  these  things. 

Can  you  describe  a  machine  so  curious  that 
it  could  never  have  been  made  without  a  great 
deal  of  thinking  and  contriving  ? 

A  man  in  England  made  two  clocks,  and 
sold  them  to  some  gentlemen,  who  sent  them 
as  a  present  to  the  Emperor  of  China.  Each 
clock  was  in  the  shape  of  a  little  chariot.  A 
very  small  lady  sits  gracefully  in  it.  Her 
right  hand  is  leaning  upon  the  chariot.  Under 
her  hand  is  a  curious  little  clock,  about  as  large 
as  a  quarter  of  a  dollar.  This  clock  strikes 


76  CURIOUS  CLOCKS. 


every  hour,  and  will  go  eight  days  without 
being  wound  up.  Upon  the  lady's  finger  sits 
a  beautiful  little  bird,  adorned  with  diamonds 
and  rubies.  Its  tiny  wings  are  spread  out 
ready  to  fly,  arid  if  a  diamond  button  below  it 
is  touched,  the  bird  will  flutter  for  some  time. 

What  makes  the  bird  move  ? 

Its  little  body  is  fall  of  very  small  wheels, 
which  make  it  move. 

How  large  is  the  whole  body  of  the  bird  ? 

About  the  size  of  a  pea. 

Can  you  tell  any  thing  more  about  the  clock- 
chariot  ? 

The  lady  holds  in  her  left  hand  a  gold  tube, 
no  larger  than  a  large  pin.  On  the  top  of 
this  tube  is  a  small  round  box.  Around  this 
box  is  a  ring,  made  with  gold  and  diamonds, 
not  larger  than  a  ten  cent  piece.  This  ring  goes 
round  and  round  the  box,  three  hours  at  a 
time  without  stopping. 

Can  you  tell  what  is  over  the  lady's  head  ? 

There  are  two  small  umbrellas,  standing 


CURIOUS  CLOCKS.  77 


upon  a  pillar  no  larger  than  a  quill.  Under 
the  largest  umbrella  is  a  little  bell,  which 
strikes  every  hour.  At  the  lady's  feet  is  a 
golden  dog,  and  before  it  are  two  little  birds, 
fastened  upon  springs.  Their  wings  and 
feathers  are  very  brilliant  with  precious  stones, 
and  they  seem  to  be  flying  away  with  the 
chariot. 

How  can  the  chariot  move  along  ? 

By  means  of  springs  and  wheels,  that  are 
out  of  sight.  If  they  are  touched,  they  can 
make  the  chariot  go  straight  forward,  or  in  a 
circle,  or  in  any  way  that  you  wish. 

What  is  behind  the  chariot  ? 

A  little  golden  boy,  taking  hold  of  it,  and 
seeming  to  push  it  along.  Above  the  um- 
brella are  flowers  and  ornaments  of  precious 
stones  ;  and  at  the  top  of  the  whole  stands  a 
\\ttlzflyingdragvn,  made  of  the  same  brilliant 
stones. 

What  good  lesson  should  we  learn  from  this 
story  ? 


78  CURIOUS  CLOCKS. 


That  the  man  who  made  these  wonderful 
docks  had  great  skill;  and  that  God,  who 
made  the  man.  and  gave  him  so  much  skill, 
must  be  more  skillful  than  all  the  men  in  the 
world — more  skillful  than  we  can  think. 


Ctodftfr. 


HIGH  would  a  sled  slide 
down  most  easily,  a  hill 
of  sand  or  a  hill  of  ice  ? 
The  hill  of  ice. 
Why  would    it  slide 
most  easily  over  that  ? 
Because  sand  is  rougher  than 
ice. 

Then  does  the  roughness  of  the  sand  hinder 
the  sled  from  sliding  down  ? 
It  does. 

What  is  the  name  that  philosophers  give  to 
this  roughness,  when  bodies  are  rubbing  against 
each  other  ? 

They  call  it  friction. 


80  FRICTION. 


Which  can  you  turn,  most  easily,  a  rusty 
lock  or  a  bright  one  ? 

The  bright  one. 

Then,  which  lock  has  most  friction  ? 

The  rusty  one. 

Why  will  a  person  slip  down  upon  ice,  and 
not  upon  stone  or  earth  ? 

Because  there  is  more  friction  when  his  feet 
rub  against  the  stone  than  when  they  rub 
against  the  ice. 

How  could  the  rusty  lock  be  made  to  turn  as 
easily  as  a  bright  one  ? 

By  oiling  it. 

Why  would  oiling  it  make  it  turn  easily  ? 

It  would  take  away  some  of  the  friction. 

How  would  it  take  away  the  friction  ? 

By  making  the  iron  smooth. 

Can  you  mention  another  example  of  fric- 
tion? 

I  have  heard  carriage  wheels  creak,  be- 
cause they  needed  greasing  at  the  axle. 

Why  do  people  grease  carriage  wheels  ? 


FRICTION. 


81 


To  make  them  smooth,  and  turn  easily 
around  the  axle. 

Why  will  the  grease  make  them  turn 
easily  ? 

It  destroys  some  of  the  friction. 


Why  do  drivers  of  carriages,  when  going 
down  steep  mountains,  fasten  one  of  the  wheels, 
so  that  it  can  not  turn  ? 

6 


82  FRICTION.' 


To  increase  the  friction  of  the  wheel,  and 
prevent  the  carriage  from  going  down  so 
fast. 

What  does  INCREASING  THE  FRICTION 
mean  ? 

Making  it  more  difficult  for  the  wheels  to  go 
down  hill. 

Horv  many  kinds  of  friction  are  there  ? 

Two. 

What  are  they  called  ? 

The  dragging  and  the  rolling  friction. 

Can  you  mention  an  example  of  dragging 
friction  ? 

The  chained  carriage  wheel,  dragged  down 
the  hill. 

What  is  an  example  of  rolling  friction  ? 

Wheels,  when  they  are  turning  or  rolling. 

When  the  walks  are  covered  with  ice,  why  is 
it  difficult  to  walk  upon  them  without  slip- 
ping ? 

Because  there  is  not  friction  enough. 


FRICTION. 


83 


What  would  happen  to  us  if  there  were  no 
friction  ? 

We  could  not  walk  a  step  before  we  should 
begin  to  slip  along  very  fast,  and  could  not 
easily  stop  ourselves. 


How  do  people  increase  the  friction  when  the 
walks  are  covered  with  ice  ? 

They  throw  sand,  or  ashes,  or  something 
rough,  upon  them. 

Could  you  hold  any  thing  in  your  hand  if 
there  were  no  friction  ? 

Not  without  difficulty. 

Why? 

Because  it  would  slip  through  so  easily. 


84  FRICTION. 

Then,  is  not  friction  very  useful  ? 

It  is ;  for  I  could  not  hold  my  knife  and 
fork,  or  book,  very  easily,  without  friction. 

How  do  people  travel  from  Mount  Cents,  in 
Europe,  to  the  town  of  Laneburg  ? 

On  the  top  of  the  steep,  snowy  precipice 
the  traveler  gets  into  a  sledge,  and  slides  down 
so  swiftly,  that  he  goes  three  miles  in  seven  or 
eight  minutes,  and  his  breath  is  almost  taken 
away  from  him  by  the  motion. 

What  makes  him  go  down  so  fast  ? 

The  ice  is  so  smooth  that  there  is  scarcely 
an}7  friction  when  the  sledge  glides  over  it. 

Why  is  it  much  easier  to  travel  and  to  carry 
heavy  loads  upon  snow  than  upon  the  ground  ? 

Because  the  snow  is  so  very  smooth,  that 
the  friction  is  almost  destroyed,  and  the  run- 
ners slide  along  more  easily  than  wheels  roll 
along  the  ground. 


fcssan   Cfjirtenttfp 


o  you  recollect  what  you 
learned  about  springs? 

I  learned  that  they 
I  were  made  by  the  water, 
under  ground,  bursting 
out  at  the  top. 
When  a  spring  bursts  out  a  little 
while,  and  then  stops,  and  then 
goes  on  again,  and  continues  stopping  and  going 
on,  what  is  it  called  ? 

It  is  called  an  intermitting  spring. 
What  is  the  meaning  of  INTERMITTING  ? 
Any  thing  that   sometimes  goes  and  some- 
times stops  is  called  intermitting. 

Can  you  tell  what  is  the  cause  of  intermit- 
ting springs  1 

They  stop   or  intermit,  at  times,  because 


86  SPRINGS. 


there  is  not  always  enough  water  under  the 
ground  to  keep  them  running. 

Why  are  not  all  springs  intermitting 
springs  ? 

Because  some  basins  are  so  large  that  they 
are  never  empty,  from  one  rain  to  another. 

Does  the  rain  make  all  springs  ? 

It  does  not. 

What  besides  rain  causes  springs  ? 

The  springs  which  are  near  those  mount- 
ains that  are  always  covered  with  snow,  are 
made  by  the  melted  snow. 

What  would  become  of  the  water  that  flows 
from  the  springs,  if  there  should  be  mountains 
and  hills  all  around  them  ? 

They  would  fill  up  the  valley  between  the 
•hills,  and  this  would  form  a  lake. 

Where  would  the  water  go,  when  the  valley 
was  filled  up  with  it  ? 

It  would  flow  out  of  the  first  opening  it 
could  find,  and  become  a  river. 


LAKES.  87 


What  can  you  tell  about  Lake  Geneva. 

The  river  Rhone  ran  down  from  the  mount- 
ains, till  it  came  to  this  valley  made  by  the 
high  hills  all  around  it,  and  there  it  stayed  till 
it  had  filled  it  and  found  an  opening,  and  then 
the  river  ran  on  to  the  ocean. 

What  is  this  valley  full  of  water  called  now? 

Lake  Geneva;  and  it  is  a  beautiful  lake, 
among  the  mountains  of  Switzerland. 

Then  what  is  a  lake  ? 

A  valley  full  of  water. 

Are  lakes  always  full  of  water  ? 

They  are  not  always  ;  some  are  dry  part  of 
the  year. 

Can  you  mention  any  ? 

Lake  Merom  is  such  a  lake,  in  Palestine. 

What  can  you  say  of  lake  Merom  ? 

It  is  a  small  lake,  made  by  the  river  Jordan, 
When  the  snows  on  Mount  Lebanon  melt, 
and  run  down  in  the  Jordan,  this  lake  is  full, 
and  is  several  miles  long  ;  but,  when  the  hot 
weather  comes  on,  it  dries  up. 


88  LAKES. 


Do  you  know  of  any  other  such  lake  ? 

In  Germany  there  is  one  called  Zirknitz 
(pronounced  Tzeerkneetz,)  lake. 

Will  you  describe  it  ? 

It  is  four  or  five  miles  in  length,  and  about 
two  miles  wide.  All  around  it  are  wooded 
mountains,  in  which  live  deer,  wild  boars,  and 
hares.  A  part  of  the  year  the  people  come 
here  in  boats  to  fish,  and  the  other  part  they 
may  sow  and  reap  grain,  and  hunt  these 
animals,  at  the  bottom  of  the  lake. 

Can  you  tell  about  a  very  curious  rvay  of 
fishing  these  people  have  ? 

When  the  water  goes  out  of  the  lake,  it 
runs  through  about  forty  holes  at  the  bottom, 
carrying  the  fish  with  it.  This  makes  so 
many  little  whirlpools.  When  the  water  has 
all  run  through,  the  peasants  go  down  with 
lights  into  one  of  these  cavities.  This  cavity 
or  hole  is  several  feet  under  the  bottom  of 
the  lake,  in  a  solid  rock.  Here  the  water 
runs  down  again,  through  small  holes,  as 


LAKES. 


through  a  seive,  and  the  poor  fishes  are  left 
behind  for  the  peasants  to  catch 

Can  you  mention  any  more  remarkable  ac- 
counts about  this  lake  ? 

Sometimes,  when  it  begins  to  rain  hard, 
three  of  these  cavities  spout  up  water  to  the 
hight  of  twelve  or  eighteen  feet.  If  the 
rain  continues,  the  water  will  bubble  out  of 
the  holes  through  which  it  had  run,  and  the 
whole  lake  will  fill  again  in  a  single  day. 


HAT  very  remarkable  lake 
do  you  read  of  in  the 
Bible  ? 

Lake  Asphaltites,  or, 
as  it  was  often  called, 
the  Dead  Sea. 

What  do  you  know  about  this 
lake  ? 

It  is  supposed  to  have  been  caused  by  the 
destruction  of  Sodom  and  Gomorrah. 
How  does  it  differ  from  other  lakes  ? 
The   water  in  it  tastes  salt,  and  different 
from  sea-water. 

What  is  found  mixed  with  the  water,  to  give 
'it  such  a  taste  ? 

Salt,  and  magnesia,  and  bitumen. 


OILY  SPRINGS.  91 


What  is  bitumen  like  ? 

It  looks  like  hard  coal,  and  burns  like 
tar. 

Do  you  know  of  any  other  wonderful  lake  in 
Asia  ? 

In  the  northern  part  of  Asia  is  a  large  lake, 
which  throws  up  a  liquid,  which  the  people 
collect,  and  put  in  their  lamps  to  hurn. 

Are  there  any  springs  in  the  world  that  throw 
up  such  liquids  ? 

In  Italy  there  are  oily  springs. 

What  can  you  say  of  them  ? 

Their  surfaces  are  covered  with  oil,  that 
smells  very  fragrant  when  it  is  burning,  and 
is  of  different  colors. 

How  much  oil  is  collected  from  some  of  these 
springs  ? 

From  one  spring,  near  the  Appenine  mount- 
ains, which  comes  out  of  a  rock,  people  can 
collect  twelve  pounds  in  one  week. 

What  is  the  name  of  this  rock  oil  ? 

Petroleum. 


92  OILY   SPRINGS. 


What  is  the  meaning  of  the  word  PETROLEUM  ? 

Petre  means  rocks,  and  oleum  means  oil. 

Why  is  it  called  rock  oil  ? 

Because  it  comes  up  from  rocks. 

Is  this  oil  ever  found  upon  the  sea  ? 

It  is  found  in  the  sea,  near  mount  Vesuvius. 

How  does  it  first  show  itself  on  the  water? 

While  it  is  rising  to  the  top  of  the  sea,  the 
water  seems  to  be  covered  with  bubbles. 

How  do  people  gather  it  ? 

They  skim  it  off,  as  they  sit  in  their  boats, 
and  then  put  it  into  pots  and  jars. 

Does  this  petroleum  rise  to  the  top  of  the 
water  all  the  time  ? 

It  rises  only  in  warm  weather. 

What  different  colors  has  the  oil? 

Some  is  white,  some  yellow,  some  red,  and 
some  black. 

Which  oil  is  the  lest  ? 

The  white,  clear  oil. 

Which  is  poorest  ? 

The  black ;  because  it  is  not  pure. 


BOILING   SPRINGS.  93 


Are  there  any  springs  of  petroleum  in  this 
country  ? 

There  is  one  in  Kentucky. 

Do  you  know  of  any  other  kinds  of  springs, 
besides  the  oily  springs,  and  springs  of  good 
water  ? 

In  Iceland  there  are  boiling  springs. 


jSSr 


Why  are  they  called  boiling  springs  ? 
Because  they  are  as  hot  as  boiling  water. 


94  MINERAL   SPRINGS. 


Are  they  of  any  use  to  the  people  of  Ice- 
land ? 

The  Icelanders  boil  and  cook  their  food 
with  them. 

What  other  springs  have  you  heard  of? 

Warm  springs. 

Why  are  they  called  warm  springs  ? 

Because  the  water  that  comes  up  from  them 
is  always  warm. 

Where  are  any  warm  springs  ? 

In  Virginia. 

What  very  useful  springs  are  found  in  the 
United  Slates? 

Mineral  springs. 

Why  are  they  called  mineral  springs  ? 

Because  they  have  sulphur,  and  iron,  and 
salt,  and  other  minerals  in  them. 

Have  they  any  different  name  ? 

They  are  often  called  medicinal  springs. 

Why  are  they  called  medicinal  springs  ? 

Because  they  cure  diseases,  as  medicine 
does. 


HOT  SPRINGS.  COLD  SPRINGS.        95 


Can  you  mention  the  names  of  some  of  these 
springs  ? 

There  are  Ballston  and  Saratoga  Springs, 
in  the  State  of  New  York,  and  Yellow 
Springs,  in  Ohio,  and  many  others  in  different 
States. 

What  curious  springs  are  sometimes  found  in 
the  sea,  near  the  shore  ? 

Springs  of  fresh  water. 

How  can  it  be  got,  without  mixing  it  with  the 
salt  sea-water  1 

A  bottle,  corked  tight,  can  be  let  down  di- 
rectly over  the  spring,  and,  when  it  is  low 
enough,  the  cork  can  be  drawn  out,  and  the 
fresh  water  will  instantly  fill  the  bottle,  which 
can  then  be  drawn  up. 

What  are  HOT  springs  ? 

Those  whose  water  is  always  hot. 

What  are  COLD  springs  ? 

Those  springs  which  are  very  cold,  in  warm 
and  cold  weather. 


96  SPRINGS. 


What  becomes  of  the  water  that  rises  from 
springs  ? 

It  runs  into  streams  and  rivers. 

Where  do  the  rivers  carry  their  water  ? 

Into  lakes  and  seas,  and  into  the  ocean. 

Does  the  water  of  springs  always  run  into 
rivers  or  lakes? 

Not  always  ;  sometimes  it  disappears,  be- 
fore it  can  get  to  a  river. 

What  becomes  of  it  ? 

Sometimes  it  is  turned  to  vapor,  by  the 
heat  of  the  sun. 

What  do  we  say  of  water,  when  it  is  turning 
into  vapor  ? 

We  say  it  is  evaporating. 

Does  the  water  of  springs  ever  disappear  in 
any  other  way? 

It  sometimes  sinks  into  the  earth,  as  the 
water  of  some  lakes  does. 

Can  you  tell  me  of  one  such  spring  ? 

In  Palestine,  near  mount  Lebanon,  there  is 
a  spring  called  Phiala,  because  it  looks  like 


SPRINGS.  97 


the  mouth  of  a  vial ;  and  the  water  from  this 
spring  goes  down  into  the  ground. 

Has  any  one  ever  found  out  what  becomes  of 
it  under  ground  ? 

In  the  life-time  of  Herod  the  Great,  the 
spring,  and  a  stream  that  came  out  of  the 
ground  thirteen  miles  from  this  spring,*  were 
examined. 

How  did  people  examine  them  ? 

They  knew  that  wood  floats  upon  the 
top  of  water;  and  they  threw  some  wood 
into  the  spring,  and  it  went  down  into  the 
ground. 

Was  it  ever  seen  again? 

The  people,  who  were  watching  the  stream 
that  came  out  of  the  ground  thirteen  miles 
south  of  the  spring,  after  looking  some 
time,  saw  those  very  pieces  of  wood  come  out 
in  it. 

What  did  this  prove  ? 

That  this  stream  ran  under  ground  thirteen 
miles. 


98  SPRINGS. 


What  is  the  name  of  this  stream  ? 

It  is  the  river  Jordan,  that  we  read  so  much 
about  in  the  Bible. 

What  do  you  learn  from  this  river  about 
streams  that  disappear? 

That  such  streams  do  sometimes  run  into 
rivers,  and  lakes,  when  we  think  they  evapo- 
rate. 

What  lad  effect  would  happen  if  the  water 
was  not  carried  off  out  of  a  lake. 

The  water  would  become  very  bad,  and  fill 
the  air  with  a  dreadful  vapor,  which  would 
make  people  sick. 


Jfiftmttfr, 


HEN  the  wind  passes  over 
stagnant  lakes  or  pools, 
and  carries  the  bad  air 
into  other  places,  what 
are  such  winds  called? 

Pestilential  winds. 
Why  are  they  called  pestilential? 
Because  they  make  people,  who 
breathe  them,  have  a  dreadful  and  dangerous 
disease,  called  pestilence. 

Are  there  any  other  remarkable  winds  ? 
There  are  very  hot  winds  blowing  from  the 
deserts  of  Arabia  and  Africa. 

By  what  names  are  these  hot  winds  called? 
Sirnoom  or  Samiel,  and  Sirocco  ;  they  have 
different  names  in  different  countries. 


100  WIND. 


What  name  is  given  to  the  hot  south  wind  in 
Egypt? 

It  is  called  Khamseen,  or  j£/?y-days' 
wind. 

Why? 

Because  it  continues  fifty  days. 

When  winds  blow  only  at  certain  seasons  or 
PERIODS  of  the  year,  what  are  they  called? 

They  are  called  periodical  winds. 

What  winds  prevail  in  Egypt  after  the 
Khamseen  is  over? 

The  rest  of  the  year  the  winds  are 
northerly. 

What  sea  is  north  of  Egypt  ? 

The  Mediterranean  sea. 

When  the  vapor  rises  from  this  sea,  where  do 
these  winds  carry  it  ? 

Across  Egypt  to  Abyssinia. 

What  becomes  of  the  vapor,  when  it  reaches 
that  country? 

The  cool  air  changes  it  to  rain,  which  falls 
in  torrents  to  the  earth. 


INUNDATIONS.  1 01 


Where  does  the  water  then  go  ? 

Some  of  it  runs  into  the  river  Nile,  and 
makes  the  river  overflow  its  banks. 

What  good  does  this  river  do? 

It  passes  through  Egypt,  where  it  never 
rains ;  and,  when  it  overflows  its  banks,  the 
whole  country  is  watered  by  it, 

How  many  times  in  a  year  does  this  river  rise 
in  this  manner  ? 

Once  only. 

What  is  this  overflowing  of  the  river  called  ? 

Inundation. 

What  would  happen,  if  there  were  no  such 
inundations. 

The  land  of  Egypt  would  be  like  a  desert, 
and  nothing  could  grow  there. 

Why  would  it  be  so  dry  and  barren  ? 

Because  they  have  no  rain,  and  all  their 
water  comes  from  this  river. 

How  does  this  show  the  KINDNESS  of  God? 

It  shows  that  He  will  provide  for  the  wants 
of  man,  in  all  countries  where  men  live. 


102 


WHIRLWINDS.     WATER-SPOUTS. 


How  does  it  show  His  POWER  ? 

We  see,  from  this,  that  He  is  able  to  bring 
water  where  it  is  needed,  even  when  it  does 
not  fall  from  the  clouds.  "He  causeth  the 
wind  to  blow,  and  the  waters  flow." 


WHIRLWINDS.     WATER-SPOUTS.  1Q3 


What  is  a  WHIRLWIND? 

A  wind  that  whirls  very  rapidly,  and  carries 
up  into  the  air  whatever  is  light  enough  to  be 
lifted  from  the  ground. 

When  it  passes  over  the  sea,  what  happens  ? 

It  raises  the  water,  and  forms  the  WATER- 
SPOUT. 

How  do  we  know  that  whirlwinds  cause 
water-spouts  ? 

A  water-spout  has  been  known  to  move 
from  sea  to  land,  and  when  it  reached  the 
land  it  became  a  whirlwind. 

When  a  whirlwind  passes  over  a  sandy 
desert,  what  happens? 

It  raises  the  sand,  arid  causes  the  Sand- 
pillar  that  travelers  speak  of. 

Are  whirlwinds  ever  mentioned  in  the  Bible  1 

The  prophet  Nahum  says,  "  The  Lord  hath 
his  way  in  the  whirlwind,  and  in  the  storm, 
and  the  clouds  are  the  dust  of  his  feet." 


HY  does  smoke  rise  from 
thejire  and  go  up  through 
the  chimney  ? 

Because  the  air  in  the 
fire-place,   when    heat- 
ed, rises  up  arid  carries 
smoke,  which  is  also  light, 
with  it. 

When  the  smoke  goes  out  of  the  chimney, 
why  does  it  not  fall  to  the  ground  ? 

Because  the  warm  air,  which  brought  the 
smoke  from  the  chimney,  continues  to  rise 
and  carry  up  the  smoke  with  it. 
What  is  this  like  ? 

It  is  somewhat  like  oil  upon  wrater. 
Why  does  not  the  oil  sink  below  the  water  ? 
Because  the  water  is  heavier  than  the  oil. 


SPECIFIC   GRAVITY.  105 


If  you  should  put  the  oil  in  the  basin  first, 
and  then  pour  water  upon  it,  would  the  oil  re- 
main  at  the  bottom  ? 

It  would  not ;  but  would  rise  through  the 
water,  and  lie  upon  the  top  of  it. 

Why  would  it  ? 

Because  the  water  is  so  much  heavier, 
that  it  sinks  down,  and  crowds  the  oil  up- 
ward. 

Why  will  not  the  smoke  spread  around  the 
chimney,  instead  of  rising  higher  ? 

Because  the  air  above  it  is  heavier,  and 
crowds  the  light  air,  which  is  filled  with  smoke, 
upward,  as  the  water  did  the  oil. 

How  high  will  the  smoke  ascend  ? 

Till  the  warm  and  light  air  that  carries  it 
comes  to  other  air  that  is  no  heavier  than 
itself. 

How  long  will  it  remain  there  ? 

Till  the  air  that  carries  it  becomes  as  cool 
as  the  air  around  it ;  and  then  the  smoke 
will  slowly  fall  to  the  ground. 


106 


BALLOONS. 


What  makes  soap-water  bubbles  rise  in  the 
air  ? 

The  light  air  that  is  in  them. 

If  you  could  fill  a  thin  bag  with  very  light 
air,  and  throw  it  into  the  air,  as  you  do  soap- 
bubbles,  what  would  it  do  ? 

The  bag  would,  rise. 

How  high  would  it  rise  ? 

Till  it  came  to  air  of  its  own  weight. 


BALLOONS.  107 


If  you  should  fasten  a  bit  of  wood  to  it, 
would  the  bag  carry  up  the  wood  with  it? 

It  would,  if  the  wood  did  not  make  the  bag 
as  heavy  or  heavier  than  the  air  around  it. 

How  are  balloons  made? 

A  light  bag  of  thin  silk,  somewhat  like  a 
very  large  bubble,  is  filled  with  a  kind  of  air 
lighter  than  the  common  air. 

How  is  this  air  kept  from  coming  out  of  the 
bag  ? 

The  bag  is  lined  with  a  varnish,  made  of 
India  rubber  and  spirits  of  turpentine,  so  that 
it  is  air  tight. 

How  can  a  person  go  up  in  such  balloons  ? 

A  little  car  is  fastened  to  the  bag,  which 
can  carry  one  or  two  persons  in  it 

How  can  a  balloon  carry  a  loaded  car  up  into 
the  air? 

The  air  in  the  bag  or  balloon  is  so  very  light 
that  it  will  go  up ;  and,  when  the  car,  with  one 
or  two  people  in  it,  is  fastened  to  the  balloon, 
the  whole  together  are  so  much  lighter  than 


108  BALLOOXS.     PARACHUTES. 


the  air  around  them,  that  they  can  no  more 
stay  down  to  the  earth  than  the  hot  air  from 
the  chimney  can. 

Do  accidents  ever  happen  to  those  who  ascend 
in  balloons  ? 

Very  often. 

How? 

When  the  balloon  comes  down,  it  sometimes 
falls  into  the  sea,  and  the  people  in  it  are  in- 
jured or  drowned ;  arid  sometimes  it  strikes 
a  tree  suddenly,  or  is  dragged  violently  along 
the  ground,  and  the  persons  in  it  get  hurt. 

How  can  a  balloon  descend  ? 

By  letting  out  some  of  the  light  air  from 
the  bag. 

How  will  this  make  the  bag  descend  ? 

There  will  be  less  light  air  in  the  bag,  to 
keep  up  the  car ;  and  so  the  balloon  will  be 
heavy,  and  descend. 

What  is  a  parachute  ? 

It  looks  like  a  very  large  umbrella,  open. 

Of  what  use  is  a  parachute  ? 


PARACHUTES. 


109 


If  a  balloon-bag  bursts,  or  a  car  upsets,  and 
the  man  in  it  has  a  parachute,  he  can  hold 
upon  the  handle  of  it,  and  keep  himself  from 
falling  quickly  to  the  ground  or  sea. 

How  will  the  parachute  hold  him  up  ? 

While  it  is  spread  out,  the  air  that  it  covers 
will  support  it  so  much  that  it  comes  down 
gently. 

How  can  you  make  a  little  parachute  ? 

By  fastening  strings  to  the  four  corners  of 
a  sheet  of  paper,  then  bring  the  four  strings 
together  in  the  middle,  and  fasten  a  light  piece 
of  wood  to  them. 


Then  what  must  you  do? 

Carry  it  to  a  high  place,  and  let  it  fall. 


110  BIRDS. 


How  will  it  fall? 

Very  slowly  indeed. 

If  you  should  have  an  open  umbrella  in  your 
hand  while  falling  or  jumping  from  a  high  place, 
would  you  fall  heavily  to  the  ground? 

I  should  not. 

Why? 

The  air  beneath  the  umbrella  would  support 
it,  and  so  keep  me  from  falling  heavily. 

How  do  birds  keep  from  falling,  when  they 
are  up  in  the  sky  ? 

They  spread  out  their  wings,  and  the  air 
supports  them. 

Is  this  the  only  reason  why  the  air  supports 
them  ? 

No;  their  bodies  contain  a  great  deal  of  air. 

How  can  they  remain  in  the  same  place  in 
the  air,  without  descending  at  all? 

They  strike  the  air  beneath  them  with  their 
wings  a  very  little,  and  then  the  air  reacts  or 
strikes  back  again  a  very  little,  and  as  long  as 
they  do  this  they  keep  their  places. 


BIRDS.  HI 


How  do  they  rise  in  the  air? 

They  strike  harder  against  the  air,  arid  the 
air  reacts  just  as  much,  and  sends  them  up 
higher. 

How  do  they  descend? 

By  partly  shutting  their  wings,  and  letting 
themselves  descend  by  their  own  weight. 

How  do  they  know  exactly  what  to  do  when 
they  wish  to  rise,  or  descend,  or  stand  still  ? 

God,  who  made  them,  has  taught  them,  and 
they  never  make  a  mistake,  or  forget  how  to 
do  it. 


o\v  are  fishes  able  to  keep 
themselves  from  sinking 
in  water? 

They  have  fins,  that 
spread  out  like  the  wings 
of  a  bird,  and  the  water 
under  them  supports  them,  as  the 
air  supports  the  wings  of  a  bird. 
But  you  said  that  the  body  of  a  bird  had  a 
great  deal  of  air  in  it,  is  it  so  with  fish? 

Fishes  have  bladders  of  air  in  their  bodies, 
that  make  them  lighter. 

How  can  they  sink  down  into  the  water,  when 
they  wish? 

God  has  given  them  the  power  of  letting 
out  the  air  from  the  bladder. 


SPECIFIC  GRAVITY.  113 


How  can  they  rise  again? 

God  has  given  them  the  power  of  filling 
these  bladders  with  air  again,  whenever  they 
choose. 

Horv  do  the  fins  of  fishes  differ  from  the 
wings  of  birds  ? 

Their  fins  are  not  so  large  for  them  as  the 
wings  of  birds  are  for  them. 

Why  are  they  not  made  as  large  ? 

Because  water  is  heavier  than  air,  and  sup- 
ports fish  better ;  so  that  fishes  need  no  larger 
fins  than  God  has  given  them. 

How  do  people  imitate  fishes,  when  they  wish 
to  go  into  the  water? 

They  take  bladders,  filled  with  air,  and  fasten 
them  around  their  bodies,  under  their  arms, 
and  the  air  keeps  them  from  sinking. 

Do  they  ever  use  any  other  light  body  instead 
of  blown  bladders? 

Cork  is  so  light  that  it  will  not  sink  in 
water,  and  people  use  it  in  the  same  way  as 
thev  do  bladders. 

8 


114  SPECIFIC  GRAVITY. 


What  are  SWIMMING-GIRDLES,  AIR-JACKETS, 

and  LIFE-PRESERVING  BELTS? 

They  are  India  rubber  bags,  filled  with  air, 
and  tied  around  the  body,  instead  of  cork  or 
bladders. 

What  is  the  danger  of  using  these  bags? 

If  they  should  slip  down  to  the  hips,  the 
heaviest  part  of  the  body  would  be  above  them, 
and  the  body  would  instantly  turn,  so  that  the 
head  would  be  down  and  the  feet  up,  'and  the 
person  would  soon  drown. 

What  are  life-boats  ? 

Boats  that  contain  tight  cells  along  their 
sides,  full  of  air. 

Why  are  they  called  life-boats  ? 

Because  they  take  people  from  a  sinking 
ship,  and  thus  save  them  from  a  watery  grave. 

If  you  should  fall  into  the  water,  what  must 
you  do  first,  to  keep  from  drowning  ? 

I  must  turn  upon  my  back,  and  stretch  my 
body  out  as  straight  as  I  can. 

What  must  you  do  with  your  hands? 


SPECIFIC  GRAVITY. 


115 


I  must  extend  them  under  the  water,  with 
my  hands  open. 

How  must  you  place  your  feet  ? 

I  must  keep  them  as  near  the  top  of  the 
water  as  possible. 


How  must  you  place  your  head  ? 

I  must  let  it  drop  back,  so  as  to  have  the 
top  of  it  nearly  covered. 

Then  what  parts  of  your  body  will  be  above 
the  water? 

Only  the  face  and  a  part  of  the  chest. 

What  must  you  do  then  ? 


116  SPECIFIC  GRAVITY. 


I  must  try  to  breathe,  so  as  to  take  more 
air  into  my  body. 

When  you  throw  out  the  air  as  you  breathe ^ 
will  not  your  body  sink  ? 

It  will,  a  little,  for  an  instant. 

What  effort  may  you  make  to  keep  from 
sinking  ? 

If  I  can  float  so,  I  must  not  make  any 
effort,  except  to  keep  my  face  out,  so  that  I 
can  breathe. 

If  you  find  your  feet  sinking,  what  must 
you  do  ? 

I  must  draw  them  up,  and  throw  them  out 
with  a  jerk. 

What  might  happen  if  you  did  not  try  to 
keep  your  feet  near  the  top  of  the  water  ? 

They  might  sink,  so  as  -to  make  my  body 
stand  in  the  water,  and  that  would  bring  my 
mouth  under  it,  and  I  should  drown. 

What  must  you  be  careful  NOT  to  do? 

Not  to  scream  or  struggle. 

When  may  you  call  for  help  ? 


SPECIFIC   GRAVITY.  H7 


When  I  am  a  little  over  my  fright. 

Who  are  the  least  likely  to  sink,  fleshy  peo- 
ple, or  those  who  are  not  fleshy  ? 

Those  who  are  fleshy. 

Why? 

Because  the  fat  part  of  their  bodies  is  so 
much  lighter  than  water. 

What  amusing  account  can  you  give  of 
Marco  Paulo? 

Marco  Paulo  lived  in  the  city  of  Naples, 
many  years  ago.  His  bones  were  very  small, 
and  he  was  very  fat.  His  body,  also,  would 
contain  a  great  quantity  of  air.  These  things 
made  him  so  light,  that  he  would  swim  on  the 
sea  like  a  duck.  When  he  stood  up  in  deep 
water,  the  water  would  not  rise  higher  than 
his  stomach.  It  is  said  that,  when  two  men 
dived  into  the  sea  to  drag  him  down  with 
them,  the  moment  they  let  him  go,  his  body 
instantly  rose  to  the  surface. 

How  can  heavy  bodies,  like  blocks  of  mar- 


118  SPECIFIC  GRAVITY. 


lie,  be  raised.,  when  they  have  fallen  into  a  har- 
bor or  river  ? 

By  fastening  casks  of  air  to  them  with 
ropes,  when  the  water  is  low. 

Why  should  the  water  be  low  ? 

Because  the  distance  between  the  marble 
at  the  bottom,  and  the  casks  at  the  top  of  the 
water,  would  then  be  the  shortest. 

How  could  it  be  raised  then  ? 

When  the  water  rises,  it  will  bear  up  the 
casks  with  it,  and  they  will  carry  up  the  mar- 
ble, so  that  it  can  be  taken  into  a  boat. 

Why  would  not  the  boat  sink,  after  the  heavy 
stone  was  placed  in  it  ? 

One  reason  is,  because  the  wood  of  boats 
is  so  light,  and  they  spread  out  over  a  large 
space  on  the  water. 


F  you  should  take  a  small 
glass  tube,  open  at  both 
ends,  and  put  one  end 
into  water,  what  change 
would  you  see  in  the 
tube  ? 

I  should  see  the  water  rise  up 
into  the  tube. 
What  makes  it  rise  ? 

The  sides  of  the  tube  draw  up  the  water 
in  it. 

What  kind  of  attraction  is  this  called  1 
Capillary  attraction. 
What  is  the  meaning  of  CAPILLARY  ? 
Hair-like. 

Why  is  this  attraction  called  capillary  at- 
traction  ? 


120  CAPILLARY  ATTRACTION. 


Because  the  bore  or  hole  through  the  tube 
is  about  the  size  of  a  hair. 

In  what  tubes  will  water  rise  highest? 

In  those  that  have  the  smallest  bore  or  hole 
through  them. 

If  you  take  two  pieces  of  flat  glass,  and  put 
the  two  lower  edges  together,  and  leave  the  up 
per  ones  a  little  apart,  and  put  the  lowe?  edges 
in  water,  what  will  happen  ? 

The  water  will  rise  up  between  them. 

What  attracts  the  water? 

The  inner  sides  of  the  glass. 

What  kind  of  attraction  is  this? 

Capillary  attraction. 

If  you  dip  one  end  of  a  piece  of  sponge  into 
water,  why  will  the  water  rise  above  that  part 
that  was  dipped  in? 

Capillary  attraction  makes  it  rise. 

What  are  the  capillary  tubes  of  sponge? 

The  little  holes  that  we  see  in  it.  Sponge 
is  full  of  large  and  smali  capillary  tubes. 

What  makes  sponge  so  useful? 


CAPILLARY  ATTRACTION.  121 


It  will  hold  a  quantity  of  water,  and  will 
drink  up  water  that  is  spilled. 

When  such  a  substance  as  sponge  drinks  up 
a  liquid,  what  do  we  say  it  does? 

We  say  it  absorbs  the  liquid. 

Then  what  does  sponge  do  to  water,  when  put 
into  it? 

It  absorbs  the  water. 

Why  will  cotton  and  linen  cloth  absorb  water? 

Because  the  cotton  and  linen  threads,  of 
which  cloth  is  made,  are  full  of  pores,  or  very 
fine  capillary  tubes,  which  attract  the  water. 

If  you  take  a  bowl  of  water,  and  lay  one  end 
of  a  towel  in  it,  what  will  happen? 

After  some  time,  the  towel  will  be  perfectly 
wet,  and  the  bowl  will  be  empty. 

Where  will  the  water  be  that  was  in  the  bowl  ? 

It  will  all  have  run  out,  through  the  towel. 

How  can  it  go  from  the  bowl  to  the  towel? 

The  tubes  in  the  linen  draw  the  water  out 
of  the  bowl. 

Of  what  use  are  wicks  in  lamps? 


122  CAPILLARY  ATTRACTION. 


They  are  a  great  number  of  capillary  tubes, 
which  draw  up  the  oil  from  the  lamp. 

Why  must  not  the  wick  be  smaller  than  the 
lamp  tube? 

Because  there  would  not  then  be  tubes 
enough  to  bring  up  the  oil. 

Why  must  not  the  wick  be  so  large  as  to  be 
crowded  tight  in  the  tube? 

If  the  wick  was  crowded  very  tightly,  the 
capillary  tubes  in  it  would  be  closed,  so  that 
the  oil  could  not  rise  through  them. 

What  happens  when  you  dip  one  end  of  a 
lump  of  sugar  into  water  or  tea? 

The  liquid  will  rise  and  fill  the  whole  lump. 

What  makes  it  rise? 

The  capillary  tubes  in  the  sugar. 

How  are  large  rocks  sometimes  split,  in  Ger- 
many ? 

Holes  are  bored  in  a  straight  line,  at  certain 
distances  from  each  other,  and  wooden  wedges 
driven  into  them. 

What  is  done  after  this  ? 


CAPILLARY  ATTRACTION.  123 


Water  is  poured  upon  these  wedges,  and 
the  pores  or  capillary  tubes  in  them  fill  with 
water. 

What  follows? 

The  wedges  begin  to  swell,  and  as  they 
pour  water  upon  them,  they  swell  larger  and 
larger,  till  they  burst  the  rock.  It  is  in  this 
way  that  grindstones  are  broken  off. 

Js  capillary  attraction  useful  in  any  other 
ways  than  those  you  have  mentioned  ? 

It  causes  the  moisture,  that  is  low  down  in 
the  ground,  to  rise  up  through  the  loose  earth, 
to  the  roots  of  plants  and  trees. 

Of  what  other  use  is  it  to  them  ? 

It  causes  the  sap  to  ascend  in  trees,  and  to 
form  beautiful  leaves,  and  flowers,  and  fruit. 

Of  what  use  is  capillary  attraction  to  our 
bodies  ? 

It  assists  in  the  circulation  of  the  blood  in 
our  bodies. 

When  sugar,  or  salt,  is  dissolved  in  a 
liquid,  what  becomes  of  it  ? 


124  SOLUBLE  BODIES. 


It  is  divided  into  such  very  small  particles 
that  we  can  not  see  them. 

How  do  you  know  that  the  sugar  is  in  the 
water,  if  you  can  not  see  it? 

Because  the  water  is  sweet  after  the  sugar 
is  put  in,  and  it  was  not  sweet  before. 

Does  the  water  rise  higher  in  the  tumbler  after 
the  sugar  is  dissolved  than  it  did  before  ? 

It  does  not. 

What  does  this  prove  ? 

That  there  are  exceedingly  small  spaces 
between  the  particles  of  water;  arid  the  par- 
ticles of  sugar  fill  up  these  spaces,  so  that  the 
water  does  not  rise  to  make  room  for  the  sugar. 

What  will  happen  when  these  spaces  are  full, 
if  you  put  in  more  sugar  ? 

The  sugar  will  sink,  and  the  water  will  rise 
in  the  tumbler. 

When  water  has  dissolved  as  much  sugar  as 
it  can,  what  do  we  say  of  it  ? 

We  say  the  water  is  saturated  with  sugar. 

If  you  should  Jill  a  tumbler  full  of  marbles , 


SOLUBLE  BODIES.  125 


could  you  pour  sand  in  it  without  taking  out  the 
marbles  ? 

I  could. 

Where  would  the  sand  go  ? 

Into  the  spaces  between  the  marbles. 

What  is  supposed  to  be  the  shape  of  the  par- 
ticles of  water  ? 

Round. 

Then,  when  you  put  sugar  into  water,  what 
is  it  like  ? 

It  is  like  pouring  sand  into  a  tumbler  full  of 
marbles. 

How  large  are  the  particles  of  water  ? 

Very  small  indeed. 

When  chalk  powder  is  put  into  water,  will  it 
dissolve  ? 

It  will  not,  but  will  only  mix  with  it. 

How  do  you  know  it  is  not  dissolved? 
,    I  can  see  it  in  the  water,  and  the  water,  in- 
stead of  looking  clear,  is  thick  and  white. 

What  is  tlit  difference  between  MIXING  a  solid 
in  water  and  DISSOLVING  it? 


126  SOLUBLE  BODIES. 


"When  a  solid  is  dissolved  it  can  not  be  seen, 
neither  does  the  water  rise  in  the  tumbler. 

How  is  it  when  mixed? 

It  colors  the  water  like  itself,  and  makes 
the  water  rise  in  the  tumbler. 

What  are  those  bodies  called  which  can  be 
dissolved  ? 

Soluble  bodies,  or  bodies  that  can  be  dis- 
solved. 

What  are  those  called  which  can  not  be  dis- 
solved? 

Insoluble  bodies. 


HAT  instrument  shows  the 
effect  of  water  pressure  ? 
A    hydrostatic     bel- 
lows. 

If  you  wish  to  make 
a    hijdro static     bellows, 
what  would  be  the  first  thing  you 
would  do? 

I  should  get  two  round  pieces  of  board,  and 
fasten  them  together  with  leather,  so  that  they 
would  rise  and  fall  together  like  common  bel- 
lows. 

What  would  you  do  next? 
I  would  take  a  long  tube,  and  fasten  it  to 
one  side  of  the  bellows,  so  that  the  lower  end 
of  the  tube  would  open  into  the  bellows. 

How  would  you  make  the  tube  stand  erect, 
after  it  was  fixed  to  the  bellows? 


128 


HYDROSTATIC  BELLOWS. 


By  bending  it  up  from  the  bottom. 

What  shape  must  the  top  of  the  tube  be  ? 

Like  a  tunnel. 

If  a  man  should  stand  upon  the  bellows  and 
pour  water  into  the  tube,  what  would  follow? 

The  upper  side  of  the  bellows  would  begin 
to  rise,  to  make  room  for  the  water,  and  raise 
the  man  standing  on  it,  higher  and  higher,  till 
the  bellows  was  full. 

What  supports  the  man  ? 

The  water  in  the  bellows. 

How  can  water  run  into  the  bellows,  while  a 
heavy  man  is  standing  upon  it  ? 

The  water  in  the  tube  presses  the  water 


HYDROSTATIC  BELLOWS.  129 


at  the  bottom  of  it  into  the  bellows,  because 
its  own  downward  pressure  is  greater  than  that 
of  the  man. 

Then  what  kind  of  pressure  does  the  down- 
ward pressure  of  water  make  ? 

Sidewise,  or  lateral  pressure. 

What  is-  the  meaning  of  LATERAL? 

Sidewise. 

Then  when  the  downward  pressure  of  the 
water  in  the  tube  presses  that  in  the  bottom  side- 
wise  into  the  bellows,  what  other  pressure  fol- 
lows ? 

Upward  pressure. 

What  causes  the  upward  pressure  of  the 
water  ? 

The  lateral,  or  sidewise  pressure. 

How  does  it  ? 

When  there  is  no  more  room  in  the  bellows 
for  the  water  to  move  sidewise,  it  must  press 
upward,  if  the  water  is  continually  running 
in,  because  it  can  go  no  other  way. 

9 


130  HYDROSTATIC  BELLOWS. 


How  could  you  let  the  water  out  of  your  bel- 
lows ? 

By  making  a  hole  at  the  bottom  of  the  tube. 

How  can  you  show  the  pressure  of  AIR  with 
the  same  instrument  or  bellows  ? 

Two  men  may  stanti  on  it,  and  one  of  them 
may  blow  hard  into  the  tube,  instead  of  pour- 
ing in  water,  and  they  will  both  be  lifted  up. 

How  can  they  keep  the  air  in  the  tube  and 
bellows  from  coming  out  ? 

By  putting  the  finger  tightly  down  upon  the 
top  of  the  tube. 

If  you  fill  a  vial  almost  full  of  water  and 
cork  it,  and  then  turn  it  up  and  down,  what  will 
you  see  moving  up  and  down  along  the  side  of 
the  vial  ? 

A  bubble  of  air. 

If  you  lay  it  on  an  inclined  plane,  where  will 
the  bubble  be  ? 

Near  the  upper  end  of  the  vial. 

Where  will  it  be  if  you  lay  it  on  a  level  table  ? 

Exactly  in  the  middle  of  the  vial. 


SPIRIT-LEVEL.  131 


How  can  you  tell  whether  a  table  is  level,  or 
inclined  ? 

By  laying  the  vial  on  it,  and  looking  at  the 
bubble,  to  see  if  it  is  in  the  middle  or  near  one 

end. 

What  useful  instrument  is  made  somewhat 

in  this  way  ? 

A  spirit-level. 

What  is  a  spirit-level  ? 

It  is  a  glass  tube,  nearly  full  of  colored 
spirit,  and  is  fitted  into  a  brass  case,  in  such  a 
way  that  the  bubble  of  air  can  be  seen. 

If  you  wish  to  find  whether  the  floor  is  level 
or  inclined,  how  must  you  use  this  instrument  ? 

I  must  place  it  on  the  floor,  and  see  wheth- 
er the  bubble  of  air  is  in  the  middle  of  the  tube. 

For  what  purpose  is  the  spirit-level  often 
used  ? 

It  is  used  in  making  roads  and  canals. 

What  are  canals  ? 

They  are  large,  long  ditches,  filled  with 
water,  that  go  from  one  town  to  another. 


132 


CANALS.     AQUEDUCTS. 


Why  are  canals  made  ? 

Because  there  are  no  rivers  in  just  the 
places  where  men  want  them,  and  so  they 
make  rivers  for  themselves,  for  boats  to  sail 
upon. 

Where  do  they  get  the  water  to  Jill  their  ca- 
nals ? 

From  the  rivers  near  them. 

What  is  done  when  a  canal  must  go  across  a 
river  ? 

They  make  tight  bridges,  which  carry  the 
water  in  the  canal  safely  over  the  river. 


CANALS.     AQUEDUCTS.  133 


What  are  such  bridges  called  ? 

Aqueduct  bridges. 

What  is  the  meaning  of  AQUEDUCT  ? 

Aqua  means  water,  and  duct  means  leader. 

Then  what  do  you  mean  by  AQUEDUCT  ? 

A  water-leader. 


Chmttutlj, 


F  /  should  take  a  glass 
lube,  open  at  both  ends, 
and  put  it  into  a,  bowl 
of  water,  and  then 
press  down  all  the  water 
around  the  tube,  what 
would  it  do? 

The  water  would  rise  up  into 
the  tube. 

What  would  make  it  rise  into  the  tube  ? 
Your  hands  would  press  down  the  water 
around  the  tube,  and  the  water  could  not  help 
rising  in  the  tube 
What  is  mercury  ? 

It  is  a  liquid  metal,  that  looks  like  melted 
silver. 

What  is  mercury  sometimes  called  ? 


QUICKSILVER.     BAROMETER.  135 


Quicksilver,  or  liquid  silver. 

If  I  should  put  quicksilver  or  mercury  into 
the  bowl,  instead  of  the  water,  and  then  press  it 
down,  would  it  rise  in  the  tube  ? 

It  would ;  but  not  as  high  as  the  water  rose, 
unless  you  pressed  upon  it  more  than  you  did 
upon  the  water. 

Why  would  it  not  ? 

Because  mercury  is  so  much  heavier  than 
water. 

If  I  could  take  all  the  air  out  of  the  tube, 
and  stop  the  upper  end,  and  put  the  other  end 
into  the  water,  would  the  water  rise  in  the  tube, 
if  I  did  not  touch  it  ? 

It  would. 

What  would  make  it  rise  ? 

The  air  around  the  tube. 

How  could  the  air  make  the  water  rise  in  the 
tube  ? 

By  pressing  down  upon  the  water  in  the 
bowl. 

What  does  this  prove  ? 


136 


BAROMETER. 


It  proves  that  the  air  has  weight. 


BAROMETER. 


What  is  the  name  of  the  instrument,  made 
of  such  a  tube  and  bowl  of  mercury  ? 

Barometer. 

What  is  the  meaning  of  the  word  BA- 
ROMETER? 

It  means  a  measurer  of  weight. 

When  the  air  is  so  heavy  as  to  press  up  the 
mercury  high  into  the  tube,  what  weather  do 
we  have  ? 

Clear,  pleasant  weather. 

Why  is  the  weather  pleasant  then  ? 

Because  the  air  is  heavy  enough  to  hold  up 
the  clouds,  and  prevent  them  from  falling 
down. 

How  can  you  tell  when  the  air  grows  lighter  ? 

The  mercury  sinks  in  the  tube. 

What  makes  it  sink  ? 

The  air  does  not  press  so  heavily  upon  the 
mercury  in  the  bowl,  and  so  the  mercury  can 
not  rise  as  high  in  the  tube. 

What  weather  do  we  have  when  the  mercu- 
ry sinks  in  the  tube  ? 


138  BAROMETER— GOOD    EFFECTS. 


Stormy  weather. 

Why  do  we  have  stormy  weather  ? 

Because  the  air  is  not  heavy  enough  to 
hold  up  the  clouds,  and  so  they  fall  down  in 
rain. 

Then  what  good  does  a  barometer  do  us  ? 

It  shows  us  what  weather  to  expect. 

Who  always  need  barometers  ? 

Captains  of  ships,  at  sea, 

Why  do  they  need  them  ? 

Because  a  sudden  storm  would  destroy  a 
ship  sooner  than  it  would  a  house. 

How  would  a  barometer  prevent  a  ship  from 
being  destroyed  ? 

The  captain  could  see  the  mercury  sinking 
in  the  tube,  and  would  immediately  prepare 
the  ship  for  the  storm,  and  thus  save  it. 

Can  you  relate  a  story  of  a  captain's  sav- 
ing his  ship,  because  he  had  a  barometer  ? 

Dr.  Arnot  gives  the  account.  He  was  in 
the  ship  at  the  time.  He  says  they  were  in 
the  southern  hemisphere.  The  sun  had  just 


BAROMETER.     GOOD  EFFECTS.  139 


mildly  set,  closing  a  beautiful  afternoon.  The 
evening  amusements  were  going  on  as  usual, 
when  suddenly  the  captain's  orders  came  to 
prepare  with  all  haste  for  a  storrn.  The  mer- 
cury in  the  barometer  had  begun  to  fall  with 
awful  rapidity.  As  yet,  the  oldest  sailors 
could  see  nothing  like  a  storm  in  the  sky,  and 
were  surprised  at  the  greatness  and  hurry  of 
the  preparations.  But  before  every  thing  was 
quite  ready,  a  hurricane  came  on  them,  more 
dreadful  than  the  oldest  of  the  sailors  had 
ever  known.  Nothing  could  resist  its  power. 
The  sails  were  torn  to  tatters,  the  masts  in- 
jured, and,  at  one  time,  the  whole  rigging 
was  near  being  destroyed.  So  loudly,  for  a 
few  hours,  did  the  hurricane  roar  above, 
the  waves  around,  and  the  dreadful  thunder 
peal,  that  no  human  voice  could  be  heard ; 
even  the  speaking-trumpet  sounded  in  vain. 

On  that  awful  night,  if  it  had  not  been  for 
the  little  tube  of  mercury  which  gave  the 
warning,  neither  the  strength  of  the  noble 


140 


BAROMETER.     GOOD  EFFECTS. 


ship,  nor  the  skill  and  activity  of  her  com- 
mander, could  have  saved  one  man  to  tell  the 
tale. 


_~^ — ^^~~~ 

gup  ow  Ugh  above  the  earth 
does  the  air  extend  ? 
Forty-five  miles. 
Then  how  many  miles 
of  air  press  down  upon 
the  mercury  in  the  bowl? 
Forty-five  miles  of  air. 
If  the  tube  was  as  large  as  a 
pump,  and  the  bowl  as  large  as  a  cistern,  would 
water  rise  in  the  tube  ? 
It  would. 

What  would  make  it  rise  ? 
The  weight  of  the  air  pressing  upo 
water  around  it, 

What  is  necessary  to  the  making  of  a  pump  / 
A  large  tube,  with  the  upper  end  closed. 


142  PUMPS. 


If  there  was  AIR  in  the  pump,  would  the 
water  rise  in  it  ? 

It  would  not. 

Why  would  it  not  ? 

Because  the  air  and  water  could  not  be  in 
the  same  place  at  the  same  time. 

If  the  top  of  the  pump  was  taken  off,  would 
the  water  rise  in  it  then  ? 

It  would  not. 

Why  would  it  not  ? 

Because  the  air  above  the  tube  could  then 
press  down  through  the  tube,  and  keep  the 
water  from  rising. 

How  could  the  air  be  taken  out  of  the 
pump. 

By  making  a  stopper  just  as  large  as  the 
hole  through  the  pump,  that  can  slide  up  arid 
down  in  it 

What  is  the  stopper  in  a  pump  called  ? 

It  is  called  the  piston.  It  has  a  hole 
through  it. 


PUMPS.  143 


What  is  there  on  the  top  of  this  stopper  or 
piston  ? 

Just  over  the  hole  in  the  piston,  there  is  a 
little  leather  cover,  fastened  so  as  to  open  and 
shut  like  a  little  door  on  a  hinge. 

What  is  this  COVER  called  ? 

It  is  called  a  valve,  or  little  door. 

WJiere  is  there  also  another  valve  ? 

In  the  lower  part  of  the  pump. 

You  said  the  air  could  be  taken  out  of  the 
pump  by  such  a  piston  as  you  have  described ; 
how  could  this  be  done? 

When  I  press  the  piston  down  toward  the 
water,  the  air  underneath  lifts  up  the  cover  or 
valve  in  it,  and  escapes  through  the  hole. 

What  will  then  be  below  the  piston? 

Nothing  but  water. 

If  you  now  raise  the  piston,  what  will  the 
water  do? 

It  will  open  the  lower  valve  and  rise  as  fast 
as  the  piston  rises. 

What  will  make  the  water  rise  ? 


144  PUMPS. 


The  air  pressing  upon  the  water  in  the 
cistern,  outside  of  the  pump. 

When  the  piston  is  pressed  down  the  second 
time,  what  will  take  place  ? 

As  it  is  pressed  down,  the  water  under  it 
closes  the  lower  valve,  and  forces  up  the  little 
valve  of  the  piston,  and  when  it  is  open,  the 
piston  can  sink  down  through  the  water. 

What  will  take  place  when  the  piston  is 
drawn  up  again  ? 

The  water  above  the  piston  will  press  upon 
the  little  valve  and  close  it,  so  that  the  water 
can  not  pass  back  through  the  piston  again. 

What  becomes  of  the  water  above  the  piston 
then  ? 

As  the  piston  rises,  it  lifts  up  this  water,  and 
throws  it  from  the  pump. 

How  could  you  raise  as  much  water  as  you 
wish  ? 

By  moving  the  piston  down  and  up  several 
times. 

How  could  you  press  down  the  pisto?i  ? 


PUMPS.  145 


By  having  a  long  pole  fastened  to  it,  with 
a  handle  at  the  top  of  it. 
What  is  the  long  pole  called? 
The  pump-handle. 
Here  is  a  picture  of  a  pump. 


How  high  will  water  rise  in  a  pump,  where 
there  is  no  air  ? 
Thirty-four  feet. 


10 


146  PUMPS. 

Why  will  it  rise  no  higher  ? 

Because  the  air  does  riot  press  heavily 
enough  upon  the  water  in  the  cistern,  to  raise 
the  Water  any  higher  in  the  pump. 

What  does  this  prove? 

It  proves  that  thirty-four  feet  of  water 
weighs  just  as  much  as  forty-five  miles  of  air 
does. 

Then  which  is  the  heaviest,  air  or  water? 

Water. 

Would  the  mercury  rise  thirty-four  feet  in 
a  tube? 

It  would  not. 

What  does  that  prove  ? 

That  mercury  is  heavier  than  water. 


•=fS=    _        — -, 


OW 


things  which    they    call 
SUCKERS? 

v       They   take    a   round 
|  piece  of  wet  leather,  and 
fasten   a   string  in   the 
center  of  it. 
How  do  they  use  it  ? 

They  press  the  leather  very  closely  to  the 
stone  which  they  wish  to  lift,  and  then,  when 
they  lift  up  the  leather  with  the  string,  the 
stone  comes  up  with  it. 

What  makes  the  stone  rise  too  ? 
When  the  string  pulls  up  the  leather,  it 
stretches  the  leather,  because  it  is  wet,  so  that 
nothing  but  its  edges  touch  the  stone. 


148  SUCTION. 


Then  what  is  between  the  leather  and  the 
stone  ? 

Nothing,  not  even  air. 

How  do  you  know  there  is  no  air  under  the 
leather  ? 

Because  the  edges  of  the  leather  are  fixed 
so  tightly  to  the  stone,  that  no  air  could  get 
under  it. 


Then  what  keeps  the  stone  and  leather  so 
tightly  together? 

The  pressure  of  the  air. 
What  does  this  prove  ? 
That  air  has  weight. 


SUCTION.  149 


What  if  the  edge  should  be  lifted  up  on  one 
side  ? 

The  air  would  get  between  the  leather  and 
the  stone 

Could  you  lift  the  stone  with  the  sucker  then  ? 

I  could  not. 

Why  could  you  not  ? 

Because  the  air  under  the  sucker  would 
press  it  up,  while  the  air  above  was  pressing 
down. 

Then  when  you  wish  to  raise  any  thing  with 
a  sucker,  may  you  have  any  air  between  the 
sucker  and  the  weight? 

I  must  not. 

How  can  a  fly  walk  upon  a  window-glass? 

Its  feet  are  much  like  suckers,  and  are  kept 
upon  the  glass  by  the  pressure  of  the  air. 

How  can  they  take  them  up  from  the  glass, 
so  as  to  walk  as  .fast  as  they  do? 

God  has  given  them  the  power  of  letting 
the  air  under  their  feet  very  quickly,  when- 
ever they  wish  to  step. 


150  FLIES.    LIZZARD.    WALRUS. 


Are  there  any  other  animals  that  walk  over 
smooth  surfaces  by  means  of  such  feet  ? 

The  lizzard,  that  lives  in  the  island  of  Java, 
walks  up  a  smooth  wall  in  the  same  way,  to 
catch  flies ;  and  the  large  walrus  walks  upon 
ice  easily,  because  his  hind  feet  are  shaped 
like  a  sucker. 

Have  any  kinds  of  fishes  this  contrivance  ? 

One  kind  of  fish  has  a  set  of  suckers  upon 
its  head,  that  enables  it  to  fasten  itself  to 
rocks,  or  to  any  thing  it  chooses. 

If  you  should  cork  an  empty  bottle,  and  let 
it  down  deep  into  the  sea,  what  would  happen 
to  the  bottle  ? 

It  would  be  crushed. 

What  would  crush  it? 

The  water  pressing  all  around  it  would 
crush  it  in. 

What  does  this  prove  ? 

It  proves  that  the  pressure  of  water  is 
greater  than  the  pressure  of  the  air. 

If  you  Jill  the  bottle  with  water,  and,  cork  it> 


SUCTION. 


and  then  let  it  down  into  the  sea,  will  it  be 
crushed  ? 

It  will  not. 

Why  will  it  not? 

Because  the  water  in  the  bottle  presses  out- 
ward so  strongly  as  to  prevent  the  pressure  of 
the  water  around  the  bottle  crushing  it. 

Jf  you  should  take  a  tight  barrel,  filled  with 
water,  and  make  a  hole  on  the  under  side  for 
the  water  to  run  out,  would  it  flow  ? 

It  would  not. 

Why  would  it  not  ? 

Because  there  would  be  nothing  to  press  it 
down. 

How  could  you  make  the  water  run  ? 

By  making  another  hole  in  the  upper  side 
of  the  barrel. 

What  good  would  that  do  ? 

It  would  make  a  place  for  the  air  above  the 
barrel  to  press  down  upon  the  water  in  the 
barrel. 

Then  when  you  wish  to  have  the  fluid  in  the 


152 


DIVING-BELLS. 


barrel  run   out   at    one  end,  what  must  you 
always  do? 

I  must  take  out  the  bung  or  stopper  at  the 
top,  to  let  the  air  come  into  the  barrel. 


What  contrivance  have  people  for  going  safe- 
ly  to  the  bottom  of  the  sea  ? 

They  can  go  in  Diving-Bells. 

What  are  they  ? 

They  are  shaped  like  a  bell,  and  are 
large  enough  for  one  or  two  persons  to  sit  in 
them. 

How  is  the  water  kept  out  of  them? 


DIVING-BELLS.  153 


They  are  let  down  into  the  water  in  such 
a  way  that  the  air  in  them  can  not  escape ; 
and  thus  the  air  prevents  the  water  from  rising 
into  them. 

How  can  you  explain  this  ? 

If  I  put  a  tumbler  into  water,  with  the  up- 
per side  down,  I  can  not  fill  it,  because  the 
air  in  it  will  not  allow  the  water  to  come  up 
into  it  too. 

How  can  the  persons  in  the  diving-bell 
breathe  1 

A  long,  flexible  tube  goes  from  the  inside 
of  the  bell  up  through  the  water,  and  the  air 
is  passed  down  to  the  men  through  it. 

What  other  contrivance  has  been  made,  for 
the  same  purpose  ? 

Instead  of  a  bell,  a  tight  cover  has  been 
made  for  the  head,  which  has  an  air-tube 
fixed  to  it.  A  man  can  fasten  this  cover  upon 
his  head,  and  put  on  a  water-proof  dress,  and 
then  go  safely  down  to  find  pearls,  or  wrecks 
of  ships,  at  the  bottom  of  the  sea. 


F  you  throw  a  stone  into 
the  water,  what  will  the 
water  do  ? 

It  will  move  in  little 
waves,  shaped  like  cir- 
cles, and  these  circles 
will  grow  larger  and  larger. 

When  the  steeple-clock  strikes, 
what  does  it  cause  the  air  to  do  ? 

It  makes  the  air  around  it  move  in  circular 
waves,  just  as  the  water  does  when  a  stone  is 
thrown  into  it. 

When  one  of  the  circles  reaches  your  ear, 
what  do  you  say  ? 

I  say  that  I  hear  the  clock  striking. 
Then  what  is  sound  ? 

Sound  is  the  effect  of  air  coming  against 
the  ear. 


SOUND.  155 


What  are  these  circular  motions,  or  waves  of 
the  air,  called? 

They  are  called  vibrations  of  the  air 

What  is  necessary  then  to  make  a  sound  ? 

Something  that  will  vibrate. 

How  is  it  known  that  sound  is  conveyed  by 
means  of  air  ? 

A  bell  has  been  rung  in  a  glass  vessel, 
when  the  air  was  taken  out  of  it,  and  it  made 
no  sound. 

If  a  cannon  should  be  fired  several  miles 
off,  would  you  hear  it  the  moment  it  was 
fired  ? 

I  should  not. 

Why  would  you  not  1 

Because  it  takes  some  time  for  the  waves 
made  by  the  cannon  to  reach  my  ears. 

What  brings  the  sound  of  the  cannon  to  your 
ears  ? 

The  air. 

Then  what  may  we  call  the  air  ? 

A  conductor  of  sound. 


156  SOUND.    AIR.    BELL. 


Why  do  we  hear  a  bell  ring  more  distinctly, 
when  the  wind  blows  toward  us  from  the  bell? 

Because  it  brings  more  waves  of  air  to  our 
ears,  than  would  reach  us,  if  the  wind  did 
not  blow  that  way. 

When  the  wind  blows  in  a  different  direction, 
how  does  the  bell  sound  ? 

Very  faint,  and  sometimes  we  can  not  hear 
it  at  all. 

Why  is  the  sound  so  faint  ? 

Because  the  wind  blows  almost  all  the 
waves  of  air  away  from  our  ears. 

If  you  strike  two  stones  together  in  water, 
can  you  hear  the  sound  as  plainly  as  you  can 
in  the  air? 

I  can,  if  my  head  is  under  the  water. 

What  does  this  prove  ? 

It  proves  that  water  is  a  good  conductor  of 
sound. 

Which  is  the  best  conductor  of  sound,  water 
or  air  ? 

Water. 


SOUND.  157 


How  can  this  be  proved  ? 

If  a  bell  should  be  rung  in  water  by  one 
person,  and  another  person  at  a  distance 
should  put  his  head  under  the  water,  it  would 
sound  much  louder  than  if  the  bell  arid  the 
person  were  out  of  the  water. 

If  you  lay  your  ear  upon  one  end  of  the  ta- 
ble, and  I  scratch  the  other  end  of  the  table 
with  a  pin,  will  you  hear  it  ? 

Yes  ;  and  it  will  sound  very  loud. 

What  does  this  prove  ? 

It  proves  that  wood  is  a  good  conductor  of 
sound. 

Why  do  animals  seem  to  know  an  earth- 
quake is  going  to  take  place  sooner  than  men 
do? 

Their  heads  are  so  near  the  ground  that 
they  hear  the  rumbling  sound  first. 

What  does  this  prove  ? 

It  proves  that  the  earth  is  a  good  conductor 
of  sound. 

Can  you  repeat  a  story  that  shows  what  good 


158  SOUND.    EARTH. 


it  has  done  to  know  that  the  earth  is  a  good 
conductor  of  sound  ? 

Many  years  ago,  there  was  a  war  in  Greece. 
The  Greeks  fought  against  the  Turks,  be- 
cause the  Turks  had  got  their  lands  away 
from  them,  and  treated  them  very  cruelly. 
In  one  of  the  Greek  cities,  there  was  a  strong 
tower.  The  name  of  the  city  \vas  Misso- 
longhi.  A  great  many  Greeks  had  fled  to 
this  tower,  to  get  away  from  the  Turks.  The 
Turks  came,  and  tried  to  destroy  the  tower. 
It  had  a  great  quantity  of  powder  in  the  cel- 
lar, for  the  Greek  soldiers  to  use.  After  try- 
ing a  good  while  to  destroy  it,  the  Turks 
went  away,  as  if  they  were  not  going  to  try 
any  more.  They  began  to  dig  a  hole  at  some 
distance  from  the  tower.  The  Greeks  did  not 
know  what  it  was  for ;  but  soon  one  Greek 
began  to  think  that  the  Turks  were  digging  a 
hole  under  ground,  to  reach  the  cellar  of  the 
tower.  He  thought  that  they  would  lay  tow 
all  along,  (from  the  powder  in  the  cellar  to 


CONDUCTORS  OF  SOUND.  159 


the  beginning  of  the  hole,)  and  then  set  fire 
to  the  tow.  This  would  burn  till  the  fire  got 
to  the  powder  in  the  cellar,  and  then  that 
would  take  fire  and  blow  up  the  tower,  and 
all  the  people  in  it. 

What  did  the  Greek  do  ? 

He  piled  up  some  stones  in  the  middle  of  the 
cellar,  or  magazine,  as  a  cellar  of  powder  is 
called,  and  put  four  smaller  stones  very  loose- 
ly upon  the  top.  Then  he  watched  those 
four  stones  till  he  saw  them  shake.  As  soon 
as  they  began  to  shake,  he  put  his  ear  down 
to  the  earth,  and  could  hear  which  way  the 
sound  came  from.  As  soon  as  he  found  out 
which  way  the  sound  came  from,  he  began  to 
dig  down,  and  soon  came  to  the  tow  that  was 
laid  there,  all  ready  to  be  set  on  fire.  This 
he  destroyed.  When  the  Turks  had  set  the 
further  end  on  fire,  they  waited  at  a  distance 
to  see  the  tower  blow  up.  When  they  found 
that  it  did  not  blow  up,  they  began  to  dig 
somewhere  else. 


160  CONDUCTORS  OF  SOUND. 


What  did  the  Greek  do  then  ? 

He  kept  watching  the  stones,  and  soon  saw 
them  shake  again.  Then  he  put  his  ear  down 
and  heard  the  noise,  and  dug  again  till  he, 
came  to  another  train  of  tow,  and  destroyed 
that. 

Did  the  Turks  try  again  ? 

They  did,  several  times ;  but  at  last  they 
began  to  think  that  the  Greeks  knew  what 
they  were  doing,  and  so  they  gave  over 
trying  to  blow  up  the  tower. 


ow  fast  does  sound  pass 
through  the  air  ? 

One  mile  in  about  five 
seconds  of  time. 

Then,   if  you  should 
see  the  flash  of  a  cannon, 
and  could  count  thirty  seconds  be- 
fore you  hear  the  first  sound,  how 
far  off  should  you  say  the  cannon  was  ? 
It  would  be  six  miles  off. 
How  could  you  tell  ? 

If  it  goes  one  mile  in  five  seconds,  it  would 
go  six  miles  in  thirty  seconds,  because  there 
are  six  times  five  in  thirty. 

If  it  should  lighten,  and  you  should  not  hear 
it  thunder  till  you  had  counted  fifteen  seconds, 


162  REFLECTION  OF  SOUND. 


how  far  off  should  you  say  the  thunder-cloud 
was? 

Three  miles  off. 

How  would  you  find  out  that  ? 

There  are  three  times  five  seconds  in  fif- 
teen seconds,  and  if  five  seconds  would  bring 
the  sound  one  mile,  fifteen  seconds  would 
bring  the  sound  three  times  as  far,  which 
would  make  three  miles. 

If  you  speak  very  loud,  what  will  the  air 
around  you  do  ? 

It  will  begin  to  move  or  vibrate  in  circles, 
that  will  spread  further  and  further. 

If  these  circles  spread  till  they  strike  against 
a  high  rock,  what  will  happen  to  them  ? 

The  rock  will  reflect  or  send  them  back, 
just  as  it  would  a  ball,  if  you  threw  one 
against  it 

If  the  circles  made  by  the  reflection  of  the 
rock  should  come  back  to  the  ear,  what  would 
you  say  ? 

I  should  say  I  heard  the  echo  of  my  voice. 


ECHOES.  163 


Then  what  is  an  ECHO  ? 

An  echo  is  sound  sent  back  again. 

What  besides  rocks  will  echo  ? 

Hills,  buildings,  and  walls  of  rooms,  if  they 
are  near  enough  and  not  too  near. 

How  near  must  they  be,  in  order  to  make  an 
echo,  when  you  speak  very  loud  ? 

So  near  that  the  circles  made  by  my  voice 
can  reach  them,  and  that  they  can  send  the 
circles  back  to  me. 

If  the  rock  should  also  send  its  circles  to  an- 
other rock,  that  would  send  them  back  to  your 
ear,  what  would  you  hear  ? 

I  should  hear  two  echoes. 

How  would  it  be,  if  several  rocks  or  surfaces 
sent  back  the  sound  at  different  instants  ? 

I  should  hear  several  echoes. 

Are.  there  any  places  where  several  echoes  can 
be  heard  ? 

There  are  many  in  the  world. 

Can  you  mention  one  in  the  United  States  ? 

At  Lake  George  there  is  a  place  where  a 


16-1  ECHOES. 


person  can  stand,  and  call  out  very  loudly, 
and  he  will  hear  several  echoes. 

What  curious  echo  is  there  in  England  ? 

At  Woodstock,  there  is  an  echo  that  will 
repeat  seventeen  syllables ,  and,  on  the  north 
side  of  the  church  at  Sussex  the  echo  will 
repeat  twenty-one  syllables. 

What  one  still  more  wonderful  can  you 
mention  ? 

In  Italy,  near  the  city  of  Milan,  there  are 
two  walls  of  a  building  that  face  each  other, 
and  a  person,  standing  at  a  window  between 
them,  can  hear  the  echo  repeat  one  word  more 
than  forty  times. 

How  is  it  when  a  pistol  is  fired  there  ? 

The  echo  repeats  the  sound  sixty  times. 

What  can  you  say  of  the  Whispering  Gallery 
of  St.  Paul's  Church,  in  London  ? 

If  a  person  whispers  very  softly  close  to 
the  wall  on  one  side  of  the  gallery,  it  will 
be  echoed  so  that,  if  another  person  puts 
his  ear  close  to  the  wall  on  the  other  side  of 


EOLIAN  HARP.     GIANT'S  HARP.  165 


the  gallery,  be  can  hear  every  word  dis- 
tinctly. 

What  is  an  Eolian  Harp  ? 

A  musical  instrument  made  with  strings. 

Can  you  describe  it  ? 

Strings  or  wires  are  stretched  very  tightly 
from  one  fastening  to  another,  and  placed 
where  the  wind  can  blow  directly  upon 
them. 

What  does  the  wind  do  to  the  strings  ? 

It  makes  them  strike  against  the  air,  and, 
when  the  circles  made  by  them  reach  your 
ears,  you  hear  very  sweet  sounds. 

What  very  large  one  TV  as  made  in  Milan, 
many  years  ago  ? 

Gattoni  stretched  seven  strong  iron  wires 
from  the  top  of  a  tower  fifty  feet  high  to  the 
house  of  Signer  Mascati. 

What  was  it  called  ? 

The  Giant's  Harp. 

Why  was  it  called  the  Giant's  Harp  ? 

Because,  when  the  wind  blew,  it  sent  forth 


166  GIANT'S  HARP. 


such  lengthened  peals  of  music :  now  it  was 
a  loud  chorus,  and  then  it  died  away  in  soft 
murmurings.  In  a  storm  it  was  heard  several 
miles. 


HEN  children  carry  fruit 
along  the  streets  in  cities, 
to  sell,  why  do  they  turn 
toward  the  houses  they 
pass,  and  put  their  hand 
up  to  one  side  of  their 

mouths,  when  they  scream  out — 

"  Strawberries  ?  " 


168  PROJECTION  OF  SOUND. 


So  as  to  make  the  sound  of  their  voices 
go  into  the  windows,  instead  of  spreading 
out  and  being-  lost  in  the  noise  of  the 


o 

streets. 


When  a  boy  is  calling  to  another,  who  is  at  a 
distance,  what  does  he  often  do  ? 

He  puts  both  hands  around  his  mouth,  like 
a  tube,  and  then  calls. 


Wlnj  does   he  put   his   hands   around    his 
mouth  ? 


SPEAKING-TRUMPETS.  169 


They  keep  the  sound  from  spreading  out, 
and  thus  make  it  go  straighter  to  the  other 
boy's  ear. 

If  the  oilier  boy  hears  the  sound,  and  turns 
around  to  know  what  is  wanted,  what  will  he 
do? 

He  will  probably  put  one  hand  to  his  ear, 
to  listen. 

Why  will  he  do  so  ? 

So  to  catch  more  of  the  sound  of  his 
friend's  voice. 

What  do  firemen  and  sea-captains  use, 
instead  of  their  hands,  to  make  their  orders 
heard  in  a  great  noise  ? 

They  use  speaking-trumpets. 


170  EAR-TRUMPETS. 


What  contrivance  have  people  for  hearing 
instead  of  putting  the  hand  to  the  ear  ? 
They  have  ear-trumpets,  or  tubes. 


How  can  deaf  people  hear  the  conversation 
of  their  friends  ? 

They  have  a  long,  flexible  tube  of  India- 
rubber,  with  a  small  ivory  opening  at  one  end, 
to  go  into  the  ear,  and  at  the  other  end  is  a 
larger  opening  made  of  ivory. 

How  is  it  used  ? 

If  I  wish  to  speak  to  the  deaf  person,  he 
puts  the  small  end  to  his  ear,  and  I  take  the 
other  end  of  the  tube,  and  speak  into  it. 

Why  will  this  help  him  to  hear  you  ? 


SPEAKING-TUBES.  171 


The  sound  goes  directly  from  mj  lips, 
through  the  tube,  into  his  ear. 

How  is  it  when  you  have  no  tube  ? 

The  sound  goes  everyway  when  it  leaves  my 
mouth,  and  so  but  little  could  go  into  his  ear. 

What  contrivance  is  made  in  houses,  by  which 
people  in  the  upper  part  can  easily  talk  with 
those  in  the  rooms  below  ? 

Tubes  are  put  into  the  walls,  with  openings 
from  them  into  the  rooms,  upstairs  and  below. 

How  are  they  used? 

If  a  person  in  the  upper  room  speaks  into 
the  tube  opening  there,  the  other  in  the  room 
below  hears,  and  goes  to  the  opening  in  his 
own  room,  and  puts  his  ear  to  it  to  listen,  and 
then  speaks  back  through  the  tube. 

Must  they  talk  very  loud  ? 

They  need  only  speak  as  if  they  were  in 
the  same  room. 

Why? 

Because  the  sound  is  kept  in  the  tube  till 
it  gets  to  the  othe  opening. 


esson 


NTO  how  many  colors  may 
light  he  separated  ? 

Light  may  be  sepa- 
rated into  seven  colors. 
What  are  the  names 
of  these  colors  1 
Violet,  indigo,  blue,  green,  yel- 
low, orange,  red. 
When  light  shines  upon  a  sheet  of  paper,  how 
can  you  see  the  paper? 

By  the  light  which  the  paper   reflects  or 
throws  back  to  my  eyes. 

Would  the  paper  reflect  ALL  the  light  that 
shines  upon  it  ? 

If  it  was  white  paper,  it  would. 
How  do  you  know  that  WHITE  paper  reflects 
ALL  the  light  that  falls  upon  it? 


COLORS.  173 


Because  it  takes  all  the  seven  colors  to  make 
white  light,  and  the  paper  looks  white,  which 
it  could  not  do  if  it  did  not  reflect  all  the  sev- 
en colors. 

How  do  you  know  that  it  takes  all  the  seven 
colors  to  make  white  ? 

Because,  if  you  separate  a  ray  of  white 
light  by  a  prism,  it  will  be  changed  into  just 
seven  colors,  and  no  more  ;  and  if  you  bring 
all  these  seven  colors  together  again,  they  will 
form  a  ray  of  white  light. 

Do  all  bodies  reflect  all  these  colors  ? 

They  do  not ;  some  reflect  one  color,  and 
some  another. 

What  becomes  of  those  colors  which  the  body 
does  not  reflect  ? 

That  body  absorbs  them. 

What  do  you  mean  by  a  body's  ABSORBING 
colors  1 

It  seems  to  take  them  into  itself,  so  that  we 
can  not  see  them. 

If  a     "body    should    absorb    all    the    col- 


174  COLORS. 


ors,  and  reflect  none,  what  color  would  it 
have  ? 

It  would  not  have  any  color. 

Then  what  should  we  call  it? 

We  should  call  it  a  black  body. 

Then  is  black  a  real  COLOR  ? 

It  is  not. 

Then,  when  we  say  a  body  is  black,  what  do 
we  mean? 

We  mean  that  the  body  has  no  color. 

And,  when  we  say  a  body  is  WHITE,  what  do 
we  mean  ? 

That  it  has  all  the  seven  colors. 

Jf  it  absorbs  all  the  colors  but  the  red,  and 
reflects  the  RED,  of  what  color  will  the  body  be? 

It  will  be  a  red  body. 

What  color  shall  we  call  it,  if  it  reflects  the 
green,  and  absorbs  all  the  rest  ? 

We  shall  call  it  a  green  body. 

How  can  you  tell  which  color  a  body  reflects, 
and  which  it  absorbs  ? 

It  will  be   of   the  color   it  reflects,    and 


COI.OKS. 


we  shall  know  it  absorbs  all  the  colors  but 
thai. 

Then  how  do  we  see  any  object? 

Bv  the  color  it  reflects  to  our  eye. 

\Vhat  is  the  reflection  of  //<////  like? 

Like  the  reflection  of  sound. 

Can  you  e.r plain  it? 

The  sun  shines  upon  a  green  leaf,  and  the 
leaf  reflects  the  green  color  to  my  eves,  just 
as  a  person  stands  out  of  my  sight  and  calls, 
and  the  rock  on  which  the  sound  of  his  voice 
falls  reflects  it  to  my  ear. 

Why  do  not  all  bodies  reflect  THE  SAMK  color 
and  absorb  the  others? 

Because  the  particles  of  bodies  are  put  to- 
gether differently ;  so  that  one  body  can  reflect 
one  color,  another  all  of  them,  and  another 
none. 

Which  would  reflect  ALL  ? 

A  white  body. 

Which  would  reflect  NONE  ? 

A  Hack  body. 


176        COLORS.  REFRACTED  LIGHT. 


If  you  should  go  into  a  perfectly  dark  room, 
and  let  in  a  ray  of  light,  through  a  small  hole 
in  the  shutter  of  the  window,  and  put  a  PRISM 
over  this  hole,  what  would  the  prism  do  to  the 
light  that  came  through  it  ? 

It  would  separate  it  into  the  seven  colors. 

Would  all  these  colors  be  mixed  together  ? 

They  would  not. 

How  would  they  be  ? 

They  would  lie  one  beneath  the  other,  very 
distinctly,  like  the  colors  in  the  rainbow. 

Then  do  they  all  go  through  the  prism  in  a 
straight  line  together? 

They  do  not ;  they  are  broken,  and  turned 
out  of  the  straight  line. 

When  a  ray  of  light  is  broken,  and  turned 
out  of  a  straight  line,  in  passing  through  a  body, 
what  do  we  say  of  it  ? 

We  say  the  light  is  refracted. 

What  is  the  meaning  of  REFRACT? 

To  break. 

WJien  is  light  REFRACTED  ? 


REFLECTION  OF  LIGHT.  177 


When  it  is  broken. 

If  you  should  put  a  piece  of  white  paper 
into  the  BLUE  ray  that  has  passed  through  your 
prism,  of  what  color  would  the  paper  be  ? 

It  would  be  blue. 

Why  would  it  be  blue  ? 

Because  it  could  reflect  only  the  blue  color 

Why  would  it  not  be  white  ? 

Because  it  must  reflect  the  seven  col- 
ors to  make  white,  and  there  is  but  one 
for  it  to  reflect  when  the  blue  alone  falls 
upon  it. 

If  you  should  put  the  paper  into  the  yellow 
ray,  of  what  color  would  it  be? 

It  would  be  yellow. 

What  does  this  prove  ? 

It  proves  that  bodies  are  of  the  color  which 
they  reflect. 

Then,  if  no  light  should  fall  on  a  body,  would 
it  have  any  color  ? 

It  would  not. 

Why  would  it  not  ? 
12 


178  REFLECTION  OF  LIGHT. 


Because  there  would  be  no  color  for  it  to 
reflect. 

When  a  body  does  not  refect  any  color,  what 
do  we  call  it  ? 

A  black  body. 

If  a  room  is  so  dark  that  no  light  can  enter 
it,  of  what  color  will  the  objects  in  the  room  be  ? 

They  will  be  of  no  color;  because  there  is 
no  color  to  be  reflected. 

Then  what  must  we  call  them  as  long  as  they 
are  in  the  dark  ? 

We  must  call  them  black  bodies. 

Can  we  ever  see  them,  when  they  are  made 
black  in  this  way? 

We  can  not ;  because  we  can  see  nothing 
when  it  is  perfectly  dark. 

Why  can  we  see  a  tree  upon  tne  top  of  a  hill 
at  a  distance,  plainer  than  we  can  see  one  on  a 
plain,,  or  in  a  valley,  at  the  same  distance  ? 

Because  the  sky  behind  the  tree  on  the  hill 
is  so  much  lighter  than  the  tree,  that  we  can 
see  the  shape  of  the  tree  very  distinctly. 


REFLECTION  OF  LIGHT.  179 


Why  is  not  the  tree  in  the  valley  as  distinct 
as  the  one  on  the  hill  ? 

Because  the  green  color  of  the  grass  be- 
hind the  tree  seems  to  mingle  with  the  green 
of  the  tree,  and  we  can  not  distinguish  the  one 
from  the  other. 

Why  can  we  see  a  WHITE  house  at  a  distance, 
plainer  than  we  can  see  a  tree  at  the  same  dis- 
tance ? 

Because  there  is  so  great  a  difference  be- 
tween the  white  object  and  the  dark  ground 
around  it. 

If  you  wish  to  make  a  room  very  light,  what 
should  you  do  besides  having  many  windows 
in  it  ? 

I  would  have  the  walls  white,  or  papered 
with  very  light-colored  paper. 

Why  would  light  paint  and  paper  make  a 
room  lighter  than  dark  paint  and  paper,  if  there 
were  the  same  number  of  windows  in  it  ? 

Because  white  walls  throw  all  the  light  that 
falls  upon  them  back  into  the  room,  and  dark 


180  REFLECTION  OF  HEAT. 


walls  absorb  some  of  the  light,  and  reflect 
only  a  part  into  the  room. 

Why  do  people,  who  have  weak  eyes,  wear  a 
shade  over  them  in  the  day  time  when  read- 
ing ? 

To  keep  the  light  that  is  reflected  from  the 
walls  of  the  room  from  coming  into  their  eyes. 

Why  do  they  wear  a  shade  when  reading  by 
candle  or  gas  light  ? 

To  prevent  the  rays  of  light  that  come  from 
the  candle  or  gas  from  entering  their  eyes. 

Is  HEAT  reflected  in  tJie  same  manner  that 
light  is  1 

It  is. 

Then  why  is  a  white  dress  so  cool  in  sum- 
mer? 

Because  it  reflects  the  heat  of  the  sun. 

Why  is  a  black  dress  so  warm  ? 

Because  it  absorbs  the  heat. 

How  can  you  prove  that  white  reflects  heat, 
and  black  absorbs  it? 

If  I  place  a  piece  of  white  and  a  piece  of 


REFLECTION  OF  HEAT.  181 


black  cloth  upon  snow,  after  sometime,  I  shall 
find  the  snow  melted  beneath  the  black,  but 
not  beneath  the  white  cloth. 

When  the  heat  of  the  sun  falls  upon  the  side 
of  a  mountain,  what  becomes  of  a  part  of  this 
heat  ? 

It  is  reflected  in  various  directions. 

If  a  valley  is  surrounded  by  such  mountains, 
will  it  be  warm  or  cold  ? 

It  will  be  warm. 

Are  there  any  such  valleys  ? 

There  are  valleys  in  Switzerland,  surround- 
ed by  such  mountains,  that  receive  so  much 
reflected  heat  from  every  side,  that  they  are 
always  green,  though  they  are  in  the  midst  of 
perpetual  snow. 


HAT  wonderful  thing  can 
be  done  by  means  of  the 
light  of  the  sun  ? 

Pictures    of    people 
can  be  made  by  it. 

What   are  such  pic- 
tures called  ? 

When  they  are  made  upon 
little  plates  of  metal,  they  are  called  daguer- 
reotypes. 

Why  do  they  have  that  name  ? 
Because  Mr.  Daguerre  first  found  out  how 
to  make  such  pictures. 

When  they  are  made  upon  PAPER,  what  are 
they  called  ? 
Photographs. 
Why  are  they  called  photographs  1 


PHOTOGRAPHS.     AMBROTYPES.  183 


Because  photos  means  light,  and  graph 
means  written  or  drawn. 

Then  what  does  photo-graph  mean  ? 

It  means  drawn  by  light. 

But  are  not  daguerreotypes  drawn  by  light 
too? 

They  are ;  but  the  names  are  different,  to 
show  the  difference  of  the  pictures. 

Can  the  pictures  be  drawn  on  glass  ? 

They  can ;  and  then  they  are  called  ambro- 
types. 

Can  the  colors  of  the  picture  be  made  too  by 
light  ? 

A  Mr.  Hill  has  found  out  a  way  to  make 
the  colors  on  the  pictures  too,  and  his  pic- 
tures are  called  Hillotypes. 

Why  do  they  have  that  name  ? 

To  show  that  it  was  a  Mr.  Hill  who  found 
out  the  way  to  make  them. 

If  you  were  going  to  have  a  picture  of  your- 
self taken,  what  would  you  do  ?. 

I  should  sit  or  stand  before  a  small  box 


184 


DAGUERREOTYPES. 


that  had  a  glass  in  the  side  toward  me,  and  I 
should  look  at  that  glass  as  I  would  into  a 
looKing-glass. 


What  is  in  the  box,  behind  that  glass  ? 

The  metal  or  paper  on  which  the  picture  is 
to  be  made. 

While  you  are  looking  at  the  glass  what  hap- 
pens ? 

A  picture  of  myself  is  made,  just  as  if  by 
looking  into  a  looking-glass  I  should  leave  a 
picture  of  my  face  upon  the  looking-glass. 


DAGUERREOTYPES.  185 


But  is  your  picture  made  upon  the  GLASS  in 
the  side  of  the  box  ? 

No  ;  it  passes  through  it,  and  is  made  upon 
the  metal  behind  it. 

Is  the  picture  as  large  as  yourself? 

It  is  very  small. 

What  makes  it  small  ? 

The  glass  I  look  at  is  so  formed  as  to 
make  things  look  a  great  deal  smaller  than 
they  are,  and  this  makes  the  picture  small. 

How  long  do  you  have  to  keep  perfectly  still 
and  look  into  the  glass  ? 

Only  a  few  seconds. 

Can  the  picture  be  made  upon  ANY  piece  of 
metal  or  paper  ? 

No ;  something  is  put  upon  it  first  to  pre- 
pare it,  to  keep  the  picture  from  passing  away. 

What  has  to  be  done  after  the  picture  is 
taken  out  of  the  box? 

When  it  is  taken  out,  the  artist,  in  some  pe- 
culiar way,  fastens  the  picture  to  the  paper, 
before  he  puts  it  into  its  frame. 


186  DAGUERREOTYPES. 


Do  we  know  whether  any  better  way  to  make 
such  pictures  could  be  found  out  ? 

We  do  not ;  because  people  are  always  try- 
ing to  find  out  better  ways  of  doing  things. 

When  any  better  way  is  found,  what  is  it 
called  ? 

It  is  called  an  improvement. 

Could  our  EYES  be  made  any  better  1 

They  could  not. 

Why? 

Because  God  made  them — it  is  only  what 
man  makes  that  can  be  made  better. 


OOK  into  my  eye,  and  tell 
me  what  you  see  ? 

I  see'  a   white   ball, 
with  a  ring  of  some  col- 
or on  the  middle  of  it, 
and  in  the  ring  a  round 
black  spot. 

Look  into  that  black  spot,  do  you 
see  any  thing  there  ? 

I  see  a  little  picture  of  my  own  face, 
as  if  I  were  looking  in  a  very  small  looking- 
glass. 

Now,  if  I  turn  my  eye  toward  a  bright  light, 
what  will  you  see  in  it  ? 

I  see  the  colored  ring  seem  to  draw  up 
around  the  black  spot,  like  drawing  up  a  bag 


188  THE  EYE. 


with  a  string,  and  the  black  spot  looks  much 
smaller. 

If  I  now  turn  away  from  the  light,  what  will 
you  see  ? 

The  ring  seems  to  spread  out,  and  the  black 
spot  looks  larger  again. 

Then  do  you  see  what  the  ring  does  to  the 
black  spot  ? 

I  do ;  it  makes  the  spot  larger  or  smaller, 
like  opening  and  shutting  a  bag  with  a  string. 

Which  part  of  your  eye  do  you  see  with  ? 

The  black  spot. 

What  is  the  name  of  the  Hack  spot  ? 

It  is  called  the  pupil  of  the  eye. 

What  is  the  name  of  the  colored  ring  ? 

It  is  called  the  iris. 

What  is  the  color  of  the  PUPIL  ? 

It  is  always  black. 

What  is  the  color  of  the  ring,  or  iris? 

It  is  sometimes  blue,  sometimes  gray, 
and  sometimes  dark  brown,  or,  as  it  is  called, 
black. 


THE  EYE.  189 


Then,  when  we  say  any  one  has  blue  or  black 
eyes,  what  do  we  mean  ? 

We  mean  that  the  iris  of  the  eye  is  blue  or 
black. 

What  is  the  use  of  the  iris  ? 

When  the  light  is  very  bright,  the  iris  keeps 
too  much  of  it  from  coming  into  the  pupil. 

Is  it  of  use  when  there  is  very  little  light  ? 

It  is ;  for  it  opens  the  pupil  very  wide,  so 
that  light  enough  may  come  into  the  eye  for 
us  to  see  easily. 

How  can  it  ? 

God  has  given  it  the  power  of  opening  wide 
in  the  dark,  to  let  in  all  the  light  it  can,  and 
then  of  almost  shutting  or  drawing  up,  when 
the  light  is  too  great. 

Why  does  it  hurt  our  eyes  to  look  at  light- 
ning at  night,  or  at  any  sudden  light  ? 

Because  the  iris  has  not  time  to  draw  up  so 
suddenly,  and  so  too  much  light  comes  into 
the  pupils. 

What  has  God  made  to  protect  our  eyes  ? 


190  THE  EYE. 


The  eyelids. 

How  does  he  give  the  eyes  rest  ? 

By  sending  the  darkness  of  night,  to  keep 
off  all  light  from  them. 

Then  is  it  well  to  sleep  with  a  light  in  your 
room  at  night  ? 

It  is  not;  because  our  eyes  need  the  rest 
that  darkness  brings,  to  keep  them  well  arid 
strong. 

Is  it  well  to  have  the  bright  sun  shining  in 
your  room  when  you  first  open  your  eyes  in  the 
morning  ? 

It  is  not ;  because  the  iris  can  not  draw  up 
around  the  pupil  quick  enough  to  keep  too 
much  light  from  corning  into  it. 

Then  how  is  the  best  way  to  have  your  bed 
placed  in  the  room  ? 

So  that  the  windows  shall  be  behind  me 
when  I  wake  in  the  morning. 

Why  can  tigers,  cats,  and  owls  see  in  the 
dark? 

Because  God  has  given  them  power  to  make 


THE  EYE.  191 


the  pupils  of  their  eyes  larger  than  ours,  and 
thus  more  light  can  come  into  them  than  can 
come  into  ours  at  night. 

Why  do  tigers  and  many  other  wild  animals 
need  to  see  better  in  the  dark  than  we  do  ? 

Because  they  seek  their  food  by  night,  while 
we  sleep. 

When  you  go  from  a  light  room  into  one 
almost  dark,  why  can  you  not  see  objects  at  first 
as  plainly  as  you  can  afterward  ? 

Because  it  takes  a  little  time  for  the  iris  of 
my  eyes  to  open  wide  enough  to  let  in  what 
light  there  is  in  the  dark  room. 


HAT  can  you  tell  me  about 
the  use  of  glass  for  see- 
ing objects  ? 

It   is  used  for  win- 
dows,   for    mirrors    or 
looking-glasses,  for 
spectacles,  for  microscopes,  and 
for  telescopes. 
What  kind  of  glass  is  made  for  windows  ? 
Glass   perfectly  plain   and   even   on  both 
sides. 

What  for  looking-glasses  ? 
The  same  kind  of  glass,  with  one  side  cov- 
ered with  quicksilver. 

What  is  the  use  of  the  quicksilver  ? 
It   reflects    whatever    is    in    front    of   the 
glass. 


GLASSES.  193 


What  kind  of  glass  is  used  for  spectacles  ? 

For  the  eyes  of  old  people,  the  glasses  in 
spectacles  must  be  made  thicker  in  the  mid- 
dle than  at  the  edges. 

How  must  it  be  for  short-sighted  or  near- 
sighted people  ? 

Their  glasses  must  be  thickest  at  the  edge, 
and  thinnest  in  the  center. 

Of  what  use  are  the  glasses  in  telescopes  ? 

They  seem  to  bring  the  moon  and  stars 
nearer  to  us,  because  they  make  them  look 
so  much  larger,  and  show  us  many  we  never 
saw  before. 

What  are  those  glasses  that  make  objects 
look  larger  called? 

They  are  called  magnify  ing-glasses. 

What  does  MAGNIFY  mean? 

Making  large  or  great. 

There  are  other  glasses  that  make  very  small 
objects  look  immensely  large,  what  are  they 
called  ? 

Microscopes. 

13 


194  TELESCOPES. 


What  is  the  meaning  of  MICROSCOPE  ? 
Micros  means  little,  and  scopeo  means  /  see. 
What  does  telescope  mean  1 


Tele  means  distant,  and  scopeo  means  /  see. 

Tell  me  something  about  the  MICROSCOPE  ? 

If  you  were  to  look  at  the  down  of  the 
butterfly's  wing  with  a  microscope,  it  would 
look  like  beautiful  feathers. 

How  would  a  drop  of  rain-water  look  ? 

As  if  it  were  full  of  large  and  strange-look- 
ing animals  or  insects. 

How  would  very  small  insects  look? 

Large  and  sometimes  very  beautiful. 


SPY-GLASSES.  195 


What  do  we  learn  by  using  a  microscope  ? 

We  learn  that  God  has  made  these  little 
creatures,  and  little  flowers,  even  those  that 
are  too  small  to  be  seen  without  a  microscope, 
just  as  perfect  and  as  beautiful  as  those  that 
are  very  large  and  splendid. 

What  kind  of  a  glass  do  sea-captains  use  ? 

They  use  a  spy -glass. 

What  is  a  spy -glass  ? 

A  glass  that  makes  distant  objects  seem 
near. 

Then  what  is  its  use  ? 

The  captain  is  able  to  see  any  distant  ship, 
or  land,  before  he  is  near  enough  to  them  to 
see  them  with  his  eye  alone. 

What  other  glass  is  the  spy-glass  like  ? 

It  is  just  like  the  telescope,  only  smaller. 

What  is  a  PRISM  ? 

A  three-sided  piece  of  glass. 

For  what  is  it  used  ? 

To  separate  the  light  that  passes  through 
it  into  its  seven  colors,  like  a  rainbow. 


,  can  we    see 


We  can. 

Caft  we  see  heat  ? 
We  can  not. 

Has  God  made  any  thing  be- 
sides heat  that  we  can  not  see  ? 
Yes  ;  he  has  made  a  wonderful  fluid  that 
can  not  be  seen,  and  yet  it  seems  to  be  every 
where. 

What  is  the  name  of  this  wonderful  fluid  ? 
It  is  called  electricity. 

If  it  can  not  be  seen,  how  do  we  know  there 
is  any  such  fluid  ? 

We  see  what  it  does,  just  as  we  see  what 
heat  does. 


ELECTRICITY.  197 


What  does  electricity  do  ? 

It  causes  the  lightning. 

What  is  lightning  ? 

It  is  caused  by  electricity  passing  from  the 
cloud  to  the  earth,  or  from  one  cloud  to  an- 
other 

How  many  kinds  of  electricity  are  there  ? 

Two  ;  and  these  always  attract  each  other. 

What  are  they  called  ? 

Vitreous  and  resinous;  they  are  also  often 
called  positive  and  negative  electricities. 

Why  does  electricity  pass  from  one  cloud  to 
another,  or  to  the  ground? 

Because  they  are  in  different  states  of  elec- 
tricity, and  so  they  attract  each  other. 

If  the  cloud  is  over  a  tall  tree,  or  church- 
spire,  what  way  does  the  electricity  take  to  pass 
from  the  cloud  to  the  ground  ? 

It  often  goes  down  the  tree  or  spire. 

Then  what  do  we  say  has  happened  to  the 
tree  ? 

We  say  it  has  been  struck  by  lightning. 


198 


ELECTRICITY. 


Then  the  tree  would  LEAD  or  CONDUCT  the 
lightning,  would  it  not  ? 


It  would ;  and  we  should  call  it  the  con- 
ductor of  the  lightning. 

Is  it  safe  to  stand  under  a  tree  in  a  thunder- 
storm ? 

It  is  not. 

Why  are  lightning-rods  fixed  to  houses  ? 

To  keep  the  lightning  from  striking  the 
house. 


CONDUCTORS  OF  ELECTRICITY.  199 


How  can  they  keep  off  lightning  ? 

Iron  draws  or  attracts  electricity,  and  thus 
the  iron  lightning-rod  conducts  the  lightning 
away  from  the  house  to  itself. 

What  becomes  of  the  lightning  then? 

The  rod  leads  or  conducts  it  down  into  the 
ground,  and  prevents  it  from  doing  any  harm. 

Is  there  any  thing  that  electricity  will  not 
pass  through  ? 

It  will  not  pass  through  glass,  ivory,  silk, 
gutta  percha,  and  several  other  substances. 

Then  how  should  a  lightning-rod  be  fastened 
to  the  house  to  keep  it  from  going  off  the  rod, 
and  injuring  the  house  ? 

It  should  be  fastened  by  something  that 
does  not  conduct  electricity 

In  what  other  way  can  you  see  the  EFFECT 
of  electricity,  or  what  electricity  does  ? 

If  I  take  a  cat  into  a  dry,  dark  room,  and 
rub  the  fur  on  her  back  with  a  piece  of  silk, 
I  shall  see  sparks  of  light,  and  hear  them 
crackle. 


200  FRICTION. 


Why  do  you  use  silk  ? 

Because  silk  keeps  the  electricity,  caused 
by  rubbing,  from  going  off  to  my  hand. 

Then  rubbing  or  FRICTION  can  produce  elec- 
tricity, can  it  not  ? 

Yes  ;  all  bodies  may  be  made  to  produce 
electricity  by  friction. 

If  you  lake  a  dry  and  warm  glass  rod  and 
rub  it  with  silk,  why  will  it  attract  bits  of  paper 
and  feathers  to  itself? 

Because  the  friction  or  rubbing  has  excited 
a  different  electricity  in  the  glass  from  what 
is  in  the  paper  or  feathers. 

Why  do  they  instantly  drop  off? 

Because,  when  they  touch,  they  are  brought 
into  the  same  state  of  electricity,  and  the  at- 
traction ceases. 

What  remarkable  stone  can  you  mention  ? 

There  is  one  which  attracts  iron  and  steel, 
called  lodestone,  and  also  magnet,  from  Mag- 
nesia, where  it  was  found. 


MAGNETISM.  201 


What  happens  if  you  nib  this  lodestone  upon 
iron  or  steel  ? 

It  gives  magnetism  to  them,  and  they  will 
also  attract  needles  or  little  pieces  of  steel  to 
themselves. 

Does  the  earth  seem  to  have  more  magnetism 
in  one  part  than  in  another  ? 

It  does. 

What  part  has  the  greatest  magnetism  ? 

That  near  the  north  pole. 

Of  what  use  is  that  magnetic  attraction  to 
us  ? 

If  a  needle  be  magnetized,  or  rubbed  with 
a  lodestone,  and  placed  where  it  can  turn 
easily,  one  end  will  point  toward  the  north. 

Why  will  it? 

Because  the  magnetism  of  the  earth,  near 
the  north  pole,  is  so  great  that  it  draws  that 
end  of  the  needle. 

Then  how  is  it  useful  to  us  ? 

It  shows  us  which  way  is  north,  when  we 
are  traveling  or  sailing. 


202  MAGNETISM. 


What  little  INSTRUMENT  or  MACHINE  do  sea- 
captains  have  to  tell  them  the  way  to  sail  their 
ships  ? 

They  have  such  a  needle  fixed  loosely  in  a 
little  box,  with  a  glass  cover  to  it,  and  by  look- 
ing at  this  needle  they  can  see  which  way 
they  are  sailing. 

What  is  the  name  of  this  useful  little  instru- 
ment ? 

It  is  called  the  mariner's  compass. 

What  toys  are  made  for  children,  to  show 
magnetism  ? 

Sometimes  little  tin  boats  are  made,  with  a 
steel  wire  at  one  end,  and  the  boat  will  float 
in  a  basin  of  water. 

How  can  the  boat  be  made  to  move  ? 

I  can  take  the  little  wire  magnet  that  comes 
with  such  boats,  and,  if  I  point  it  toward  the 
steel  wire  at  the  end  of  the  boat,  it  will  move 
toward  my  magnet,  and  so  I  can  draw  it  all 
around  the  basin. 

Are  there  any  other  such  toys  ? 


MAGNETISM. 


203 


Sometimes  little  glass  ducks  and  fishes  are 
made  with  a  bit  of  steel  in  their  mouths,  and 
they  will  be  drawn  to  the  magnet  in  my  hand 
in  the  same  way. 


-    irst. 


ou  told  me  that  all  bodies 
may  be  made  to  produce 
electricity   by  friction; 
can   electricity   be  pro- 
duced in  any  other  way  ? 
It  can,  by  means  of 
metals    and    a    peculiar    liquid 
called  an  acid. 
Can  you  explain  how  it  is  done  ? 
When  certain  different  kinds  of  metals  are 
put  into  an  acid,  and  then  these  metals  are  con- 
nected by  a  wire,  a  peculiar  kind  of  electric- 
ity will  be  made  to  pass  along  the  wire,  from 
one  metal  to  the  other. 

How  long  will  this    electricity   continue   to 
pass  ? 


ELECTRICITY.  205 


As  long  as  the  metals  remain  in  the  acid 
and  are  connected  by  the  wire. 

How  long  may  the  wire  be  which  connects  the 
metals  and  carries  the  electricity  ? 

As  long  as  we  choose  to  make  it. 

Which  way  would  the  electricity  move  ? 

It  could  go  either  way,  though  not  at  the 
same  instant. 

How  could  the  electricity  be  kept  from  passing 
off' from  the  wire  ? 

By  covering  the  wire  with  gutta  percha,  or 
something  that  does  not  conduct  electricity. 

How  could  it  be  stopped  in  passing  along  the 
wire  ? 

By  putting  to  it  another  wire,  or  any  thing 
that  conducts  electricity,  or  by  cutting  the 
wire. 

Where  do  we  see  such  wires  ? 

The  telegraph  wires  that  we  see  fastened 
to  tall  posts  are  such  wires. 

Where  are  the  ends  of  these  wires  ? 

One  end  of  the  wire  is  generally  in  a  .house 


206  ELECTRICITY. 


in  some  large  city,  like  New  York,  and  the 
other  in  another  city,  like  Washington  or 
Boston. 

How  fast  does  the  electricity  go  from  one 
end  of  the  wire  to  the  other  1 

It  seems  to  take  no  time ;  but  the  instant 
it  starts  it  seems  to  be  at  the  other  end. 

What  wonderful  instrument  is  fixed  at  each 
end  of  the  telegraph  wire  ? 

Mr.  Morse  has  contrived  an  instrument  to 
make  marks  by  means  of  the  electricity. 

What  is  the  use  of  these  marks  ? 

Each  mark  stands  for  some  letter  of  the 
alphabet. 

What  is  done  with  these  marks  ? 

Some  one  writes  out  the  letters  they  stand 
for  on  a  piece  of  paper,  thus  : — 


Tell          J       o     h      n. 

Of  what  use  is  all  this  ? 

A  person  at  the  instrument,  in  New  York, 


ELECTRICITY.  207 


can  make  the  electricity  pass  along  the 
wire  to  the  Washington  instrument,  and 
scratch  the  letter-marks  on  the  paper  there. 

Then  what  will  be  done  in  Washington  ? 

The  person  at  the  instrument  there  will  read 
the  words,  and  then  send  back  electricity 
along  the  wire,  which  will  write  his  answer 
in  the  office  in  New  York. 

What  more  wonderful  instrument  has  Mr. 
House  made  ? 

He  has  made  an  instrument  that  prints  the 
letters  themselves. 

What  does  it  look  like  ? 

It  looks  a  little  like  a  piano,  with  a  small 
machine  on  the  top  of  it. 

How  is  it  used  ? 

A  gentleman  sits  before  it,  as  if  he  were 
playing  the  piano.  As  he  touches  the  ivory 
keys,  the  electricity  passes  along  the  wire  to 
Washington,  and  the  instrument  there  begins 
to  print  the  letters  that  each  key  makes. 

What  are  these  letters  printed  upon  ? 


208  ELECTKICITY. 


They  are  printed  upon  a  narrow  strip  of 
paper,  that  rolls  off  a  little  wheel  as  fast  as  it 
is  wanted. 

What  is  done  with  this  strip  of  paper  ? 

It  is  cut  off,  and  sent  wherever  it  is  direct- 
ed ;  and  then  the  instrument  is  ready  for  an- 
other message. 

Why  is  this  way  of  writing  letters  to  people 
very  convenient  ? 

Because  people  can  talk  together  about 
their  business,  without  losing  any  time,  just 
as  if  they  were  in  the  same  room. 

Are  there  many  telegraph  wires  ? 

Yes  ;  all  the  large  cities  have  them. 

What  was  the  most  wonderful  telegraph  wire 
ever  made  ? 

The  one  that  stretched  across  the  Atlantic 
ocean. 

Are  there  telegraph  wires  in  other  countries  ? 

There  are ;  and  the  time  may  come  when 
people  in  every  part  of  the  world  can  talk  to- 
gether, by  means  of  them. 


mint   CHrtg-jJmiilL 

ow  high  from  the   earth 
the  atmosphere  ex- 


More   than   forty-five 
miles. 

jFVowz  what  does  all  our 
light  come  ? 

It  comes  from  the  sun. 
When  the  rays  of  light,  in  coming  from  the 
sun,  enter    the    atmosphere,  what  happens   to 
them  ? 

They  are  refracted   or  broken,  and  turned 
out  of  their  course. 
What  refracts  them  ? 
The  atmosphere. 

Does  it  also  separate  the  light  into  different 
colors,  like  the  prism  ? 

It  does  not ;  it  only  breaks  them. 


210  KEFRACTED  LIGHT. 


If  the  atmosphere  becomes  more  DENSE  or 
THICK,  how  would  the  light  be  refracted  ? 

It  would  be  refracted  more  and  more,  the 
more  dense  the  atmosphere  becomes. 

When  light  passes  through  a  prism,  which 
colored  ray  is  refracted  the  most,  or  turned  the 
furthest  out  of  its  course  ? 

The  violet. 

Which  is  refracted  the  least  ? 

The  red. 

What  is  it  that  refracts  the  light  ? 

The  glass,  of  which  the  prism  is  made. 

If  light  passes  through  water,  is  it  refracted 
more  or  less  than  when  it  passes  through  the 
atmosphere  ? 

It  is  refracted  more. 

Why  does  water  refract  light  more  than  the 
atmosphere  ? 

Because  it  is  more  dense  than  air. 

Then  what  bodies  refract  light  most  ? 

The  densest  bodies  through  which  light 
can  pass  refract  it  most. 


REFLECTED  LIGHT.  2ll 


Why  does  the  sky  or  atmosphere  look  Hue  1 

The  rays  of  light  come  from  the  sun,  pass 
through  the  atmosphere  to  the  earth,  and  are 
reflected  back  through  the  atmosphere,  and 
the  blue  rays  are  stopped  on  their  way,  and 
reflected  again  to  our  eyes. 

What  becomes  of  the  other  colors  ? 

They  pass  on  through,  without  being  re- 
flected. 

Why  are  the  blue  rays  stopped  ? 

Because  they  do  not  seem  to  have  moment- 
um enough  to  carry  them  through. 

What  did  you  say  was  the  meaning  of  MO- 
MENTUM? 

Moving  power ;  or  weight  and  speed  put 
together. 

Then  what  do  you  mean  by  the  momentum 
of  a  blue  ray  ? 

Its  power  to  carry  itself  through  the  atmos- 
phere. 

Which  color  has  the  greatest  momentum? 

The  red. 


212  OPAQUE  BODIES. 


If  the  atmosphere  should  become  very  thick 
or  dense,  what  would  be  the  effect  upon  the  light 
that  passes  through  it  ? 

None  of  the  rays  but  the  red  would  have 
momentum  enough  to  pass  through  the  at- 
mosphere. 

When  does  the  sun  look  red  ? 

When  it  is  seen  through  a  fog  or  vapor. 

If  the  atmosphere  did  not  reflect  any  of  the 
suris  rays,  how  would  the  sky  appear  ? 

Perfectly  black. 

When  bodies  do  not  allow  any  light  to  pass 
through  them,  what  do  we  call  such  bodies  ? 

Opaque  bodies. 

Can  you  mention  an  opaque  body  ? 

A  piece  of  wood,  or  marble,  or  iron,  is 
opaque. 

How  can  you  tell  ? 

By  holding  them  up,  to  see  whether  the 
light  will  pass  through  them. 

When  a  body  permits  light  to  pass  through 
it,  what  kind  of  a  body  is  it  called? 


TRANSPARENT  BODIES.  213 


A  transparent  body. 

Will  you  mention  some  transparent  "body  ? 

Glass  is  transparent. 

Why  is  it  transparent  ? 

Because  light  can  pass  through  it. 

Is  water  transparent  ? 

It  is. 

Then  why  is  it  more  difficult  to  see  bodies 
distinctly  through  a  fog  than  when  the  air  is 
clear  ? 

The  fog  refracts  these  rays  of  light  that 
bodies  reflect  through  it  so  much  more  than 
air  does,  that  we  can  not  distinguish  the  size 
and  shape  of  those  bodies  very  well;  they 
seem  much  larger  than  they  really  are. 

Can  you  relate  a  story  about  a  singular  mis- 
take caused  by  a  dense  fog  or  mist  ? 

A  shepherd,  upon  one  of  the  Cumberland 
mountains,  in  Europe,  was  suddenly  sur- 
rounded j  with  a  thick  fog.  Every  thing 
seemed  so  very  large  that  he  lost  his  way. 
He  tried  to  find  some  object  that  he  knew, 


214  SPECTER  OF  THE  BROCKEN. 


and  by  which  he  could  find  where  he  was, 
and  where  he  ought  to  go.  He  soon  came  to 
what  seemed  to  be  a  very  large  mansion, 
which  he  did  not  remember  of  having  seen 
before.  He  went  into  it  to  inquire  the  way 
home,  and  there  found  his  own  family.  It 
was  his  own  cottage.  The  fog  had  deceived 
him  so  much  that  it  was  some  time  before  he 
could  believe  the  fact. 

Do  clouds  ever  reflect  shadows  of  objects 
that  are  before  them  ? 

They  do. 

Will  you  mention  one  instance  ? 

Many  years  ago,  a  Mr.  Hane  went  up  the 
Hartz  mountains,  in  Germany,  at  a  place 
called  the  Brocken.  As  he  looked  toward 
the  south-west,  he  saw,  at  a  very  great  dis- 
tance, the  figure  of  a  man  as  large  as  a  giant. 
Just  then  a  gust  of  wind  almost  blew  off  his 
hat,  and  he  raised  his  hand  to  his  head  to 
keep  on  his  hat.  The  figure  did  the  same. 
He  then  bent  his  body,  as  if  to  salute  it  The 


SPECTER  OF  THE  BROCKET.  215 


figure  returned  it  at  the  same  instant.  He 
then  went  back,  and  took  another  man  with 
him.  They  then  saw  two  such  giant  figures  ; 
and  all  that  these  men  did,  the  figures  imi- 
tated. 

What  was  the  cause  of  this  appearance  ? 

When  the  sun  is  rising  or  setting,  and 
throws  his  rays  over  the  Brocken,  upon  the 
fine,  light  clouds  floating  around,  if  a  man 
comes  between  the  rays  of  light  and  the 
cloud,  the  shadow  of  the  man  will  be  seen  on 
the  clouds  opposite  him,  and  all  his  motions 
will  be  represented  by  his  shadow. 

How  large  will  his  shadow  be  ? 

It  may  extend  jive  or  six  hundred  feet. 

How  far  from  the  man  will  it  he  ? 

Two  miles  off. 

What  name  have  the  people  in  that  country 
given  to  this  immense  shadow  ? 

They  call  it  the  Specter  of  the  Brocken. 


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NATURAL  PHILOSOPHY— PART  SECOND.     By  Mb 
A.  SWIFT,  formerly  Principal  of  the  Litchfiold  Female  Se         ^ 
From  the  notices  in  his  possession,  he  would  ".all  the  atten  .^,7 
Teachers  and  others  to  the  following : 

From  the  H^fi/^rd  Watchman. 
1(,fif    f  ,in  wri  •  o  '-  child's  book  of  natu,«t  euicu-i 

I    fnn? Htft1-*11*5'  ' '    ;'er  ?'    mer  VV°rk   l°    the   mi"dS   Of  «*M«--    ft- 

w  tJ  S rt,  ^        «urpu,ses  it  m  sor-  e  respects.    Children  are  better  r  ,«a; 

with  idea,  than  words  ;  and  it  would  not  be  easy  to  find  a  spare  word  in  the   -  b 
of  th'.s  1'ttle  book.    It  is  beautifully  concise  and  simple. 
From  the  New  Haven  Palladium. 

tr^7S"S9thLadmi?rIy  arap!ed  u°  tbeir  "Pacitfes,  the  science  bein,  ill, 
trnted  by  the  things  most  familiar  to  their  sight  and  undirstandin*  The  ?<  PI 
x art  of  the  same  work  was  extremely  well  revived. 

From  the  New  York  Weekly  Messenger. 

So  simpie,  plain,  ea?7,  instructive  and  entertaining,  that  the  child  under 
.f  a  su  table  teacb-r,  15  anxious  to  go  forward  until  the  whole  is  ler  me ' 
.he  task,  of  children  are  thu&  renderc  1  pleaS:ng  Instead  of  painful,  there  ,-  ,r  or 

(•••*>(  but  a  c-rta..ity  of  imj)rovem..:)t. 

I-'rom  the  Connecticut  Observer. 

This  liti'j  vl.i.':»  i»  an  admirable  counterpart  to  t',  a  tir«f  that  wn-^ 
.nd  which  t   hibited  the  tact  of  the  writer  for  addrewin?  youthf-  1  m?r 


nt    ) 


"   fe 


tt  C8n  he  !nade 


who,  io  the  -rarly  developinciiU  ,.|  ihoufh\7  wiin'to'rnquire 
|  tnmgs,  and  are  /--i'l  uf  curiosity  vith  reg.  -<\  to  the  objecta  • 


•  y!e  .     it  sLo 
'  brightly  p 

-„  '.hat  mi 


modes  of  explanation  are  very  judi,  ,>us  TI 
the  chain  of  consecutive  ret  oning  clenr' 
ter  of  rejoicing  to  all  parents  and  teacHoio 
writer,  are  devoting  their  powers  to  such  wcj 
liternture  of  the  country. 

From  the  Fall  Rhfr  J,fcn     , 
These  less,  ns  are  admirably  adapted  to  the  capacit:?»  of  chil<-;cn.    P.VR 


MUhe  I, 

lit  SU  '- 

inj,   o'ho:e 

ito  the  tense  of 
";    ;  the 

and 
mat- 


SitD. 

•d.  r 

^e  th 
Iu  the 


-rthe 
i 


From  the  Jfew   York  Plaindcalcr. 

'Inis  book    i  obv'ously  the  production  of  one  who  undfrstands  the  wa   u  ar  , 
,apaclt,es  of  yen-  young  students,  and  what  is  more  rttie,  understaJ    how* 
Lceojnmodare  I    rself  to  their  immature  intellect* 


